Softomate Solutions is a London-based software development studio that builds bespoke web applications for UK businesses. We are asked the SaaS-versus-custom question almost daily, and we will give you the honest answer: SaaS wins in many situations. What this guide covers is the full decision framework, the hidden economics, and the conditions under which building custom pays for itself, so you can make the right call for your business rather than whichever option a vendor is trying to sell you.
SaaS is the correct answer when your requirement maps cleanly onto a commoditised process that thousands of businesses share. Accounting, payroll, email marketing, help desk ticketing, project management, HR administration, video conferencing - these are problems that have been solved well by existing platforms. The marginal cost of adding your business to an existing platform is negligible. The marginal cost of building your own is not.
SaaS wins clearly under these conditions:
Custom web application development wins when your workflow is genuinely different from the market, when competitive advantage depends on the software itself, or when the long-term economics of SaaS become punishing at your scale.
Custom wins clearly when:
SaaS vendors publish per-seat per-month pricing that looks affordable at five users and alarming at fifty. The compounding of per-seat costs is the most common reason UK businesses eventually commission custom development after years of SaaS spending.
Consider a mid-market UK business running its operations on a SaaS stack:
Total: approximately ยฃ4,050 per month, or ยฃ48,600 per year. Over three years: ยฃ145,800. That does not include onboarding, training, data migration costs when you switch, or the price of workarounds for the things the SaaS tools cannot do.
Beyond per-seat pricing, SaaS lock-in has its own cost. Migrating away from Salesforce is a project that routinely costs ยฃ20,000 to ยฃ60,000 in data cleaning, migration engineering, and staff retraining. Vendors know this, which is why they increase pricing by 10 to 20 per cent annually for established accounts. The switching cost is real and rarely appears in the initial business case.
The crossover calculation is simple in concept. Build it in a spreadsheet before making any decision:
SaaS 3-year total cost = (Monthly subscription x 36) + integration costs + migration costs + workaround costs + annual price increase buffer (assume 15% compounding)
Custom 3-year total cost = Build cost + year 1 hosting/maintenance + year 2 hosting/maintenance + year 3 hosting/maintenance + enhancement budget
Custom software typically costs ยฃ800 to ยฃ2,000 per year in hosting and monitoring for a modest application on AWS or GCP. A maintenance retainer with a UK development team runs ยฃ1,500 to ยฃ4,000 per month depending on application complexity and required response times.
A realistic example: a UK professional services firm with 40 users spending ยฃ3,500 per month on a fragmented SaaS stack. Over three years, with 15% annual price increases, total SaaS cost approaches ยฃ170,000. A custom application consolidating those workflows costs ยฃ65,000 to build and ยฃ30,000 to maintain over the same period. Break-even is reached at approximately 22 months. From month 23, the business is saving money.
Run this calculation honestly. Include the hidden SaaS costs. If custom does not cross over within 36 months, SaaS is probably the right answer for now.
The binary choice between all-SaaS and all-custom is a false dichotomy. Most mature UK businesses operate hybrid architectures:
The best hybrid strategies are driven by an honest assessment of where SaaS adds genuine value and where custom software creates genuine differentiation. Commissioning API development to connect your SaaS tools properly is often a far better investment than replacing them with a monolithic custom system.
Most UK businesses evaluate SaaS tools by booking a demo and checking whether the feature list covers their obvious needs. This approach consistently misses the issues that cause problems six to twelve months after signing a contract. A more rigorous evaluation covers:
Data portability. Can you export all your data in a usable format at any time, not just on cancellation? Request a sample data export during the trial. If a vendor resists this, that tells you everything about how they view your data.
API completeness. If you will ever need to integrate this platform with another system, evaluate the API thoroughly. Does it expose all the data you need? Does it support webhooks for real-time events? Is the rate limiting acceptable for your integration's call volume? Shallow APIs create expensive custom integration workarounds.
Pricing trajectory. Research the vendor's pricing history. Many SaaS platforms offer attractive introductory pricing and then increase substantially. Ask explicitly whether your pricing is locked, and for how long. Understand exactly what triggers a tier upgrade - a sudden jump from 25 to 26 users should not double your monthly bill.
Downtime and reliability record. Every SaaS vendor publishes a status page. Review the historical incident record, not just the uptime percentage. Frequent short incidents affect productivity more than the percentage suggests. Verify whether the SLA actually means anything - most SaaS SLAs offer a month's service credit for downtime, which is rarely meaningful compensation for real business disruption.
Support quality. Trial the support during your evaluation period. Ask a complex question and time the response. Check whether support is included in your tier or costs extra. Enterprise-grade support frequently adds 20 to 30 per cent to the headline subscription price.
Before spending money in either direction, work through these questions:
Is there a SaaS tool built specifically for our vertical? If yes, pilot it for 90 days before commissioning custom work. Vertical SaaS often has depth that horizontal platforms cannot match.
What happens to our data if the SaaS vendor is acquired or closes? This is not paranoia - it happens regularly. Your data export strategy should be defined before you sign a SaaS contract, not after.
Do our data residency obligations restrict which SaaS platforms we can use? UK GDPR and sector-specific regulations (FCA, NHS Data Security, Legal Aid Agency) sometimes create hard constraints. Know these before evaluating platforms.
What is the realistic three-year SaaS total cost including all seats, integrations, and price increases? Do the calculation honestly.
If we build custom, what is our maintenance plan? Custom software requires ongoing maintenance. Either an in-house team or a retained development partner. Custom software with no maintenance plan is not an asset; it is a liability accumulating interest.
SaaS is cheaper in years one and two for most businesses. At scale, with many users or heavy reliance on premium SaaS tiers, the economics often reverse. A business paying ยฃ4,000 per month for SaaS tools will spend ยฃ144,000 over three years. A custom system solving the same problems might cost ยฃ60,000 to ยฃ80,000 to build and ยฃ15,000 per year to maintain, producing net savings from year two or three onwards. The honest calculation requires including all SaaS costs, not just headline subscription fees.
SaaS tools deploy in days or weeks. A custom web application takes three to six months for a focused MVP and six to eighteen months for a complete product. This timeline difference is a legitimate factor in your decision. If you need operational capability within sixty days, SaaS wins on speed regardless of long-term economics. If you are planning your technology stack for the next three to five years, the SaaS deployment speed advantage shrinks considerably in the overall decision.
Data migration from SaaS platforms is almost always more complex than vendors suggest. Before signing any SaaS contract, verify that you can export your data in a machine-readable format (CSV, JSON, or via API) at any time, not just on cancellation. Document what data lives where. When moving to custom software, budget for a migration project: data cleaning, transformation, and validation typically takes two to four weeks for a mid-sized dataset, and longer if the data quality is poor.
Yes, and this is often the most pragmatic answer for growing UK businesses. Stripe for payments, Xero for accounting, and HubSpot for CRM are genuinely excellent products. Building custom software around them via their APIs gives you the best of both worlds: commodity reliability from established platforms, and bespoke functionality where your workflows diverge from the standard. The condition for this working well is that your custom software team understands API integration thoroughly.
Three practices reduce SaaS lock-in meaningfully. First, never use a SaaS platform's proprietary automation or workflow engine for logic that belongs to your business - keep that logic in your own systems or in code you control. Second, treat SaaS APIs as the integration layer rather than your data of record wherever possible - your authoritative data should live somewhere you can fully export. Third, run quarterly data export tests to confirm you can retrieve everything you have stored, and keep those exports in a format your team can actually use.
Most SaaS-versus-custom decisions focus on the build cost versus the subscription cost, which is only half the picture. Total cost of ownership (TCO) over a three-to-five-year horizon includes every cost category that changes as the business grows:
Customisation cost. SaaS platforms rarely do exactly what a growing business needs without customisation. Zapier workflows, custom fields, API integrations built and maintained by a freelancer, and workarounds that require manual steps all carry a cost that compounds over time. A business spending four hours per week on manual data entry to compensate for a SaaS limitation is spending roughly 200 hours per year - which at a staff cost of ยฃ25 to ยฃ40 per hour amounts to ยฃ5,000 to ยฃ8,000 annually in hidden labour cost alone.
Vendor price increase risk. SaaS pricing is not fixed. Salesforce, HubSpot, and Zendesk have all significantly increased pricing over the past five years. A sensible TCO model includes a 15 to 20 per cent annual price increase buffer for any SaaS platform on which the business becomes operationally dependent. This is not pessimism - it is the observed market reality for established B2B SaaS vendors.
Training and turnover cost. Every time a member of staff joins or leaves, SaaS tool training is required. Custom software built around your actual workflows can be more intuitive for new users because it matches the language and processes your team already uses, rather than imposing a generic vendor framework.
Opportunity cost of a poor fit. This is the hardest to quantify but often the most significant. If your software does not support your best process, your people adapt their process to the software. That adaptation has a real cost in efficiency, quality, and competitive differentiation. A custom system built around your best practice enforces and scales it; a SaaS tool built around the industry average converges your process toward the average.
Working through TCO honestly, across all cost categories and over five years, is the only reliable basis for this decision. Businesses that make the SaaS-versus-custom choice based on the first-year subscription cost versus the build quote alone consistently end up reassessing the decision at scale.
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