When Should an Enterprise Build Custom Tools vs Buy SaaS?

The Short Answer

Buy SaaS when the tool does exactly what you need, the per-seat economics work at your scale, and the vendor’s roadmap aligns with your needs. Build custom when you are paying for a platform you barely use, your workflows do not fit the SaaS model, or per-seat licensing is bleeding you dry.

The breakeven point is more predictable than most people think. If a SaaS tool costs more than £50K/year and you use less than a third of its features, a custom replacement almost certainly pays for itself within 18 months.

Who This Is For

Enterprise leaders making software procurement decisions — CTOs, CIOs, heads of operations, or finance directors questioning whether the organisation’s SaaS spend is delivering proportional value.

This is not for you if:

• You are evaluating commodity tools (email, Slack, basic office suite) — always buy these
• Your total software spend is under £100K/year (the build option rarely makes sense at this scale)
• You do not have access to competent developers, either internally or via an agency

The Decision Framework

After helping dozens of enterprises with this exact question, we have distilled it into five factors that reliably predict whether building or buying is the right call.

Factor 1: Feature Utilisation

The question: What percentage of the SaaS platform’s features does your organisation actually use?

• 70%+ utilisation: Buy. You are getting real value from the platform’s breadth.
• 30-70% utilisation: Evaluate. Could you get the same value from a lower tier, a cheaper competitor, or a focused custom build?
• Under 30% utilisation: Build. You are subsidising features you will never touch.

This is the single most predictive factor. We consistently find that enterprises use 15-25% of their major SaaS platforms’ capabilities. Salesforce, ServiceNow, Workday — the pattern is the same. Massive platforms with enterprise pricing, used as expensive versions of much simpler tools.

Factor 2: Workflow Fit

The question: Does the SaaS platform’s data model and workflow logic match how your business actually operates?

Every SaaS product encodes assumptions about how work should flow. Salesforce assumes your world revolves around accounts, contacts, and opportunities. ServiceNow assumes ITIL-aligned service management. Workday assumes HR processes that match their model.

When your processes align with these assumptions, SaaS is brilliant. When they do not, you spend more time configuring workarounds than doing actual work. The telltale signs:

• Your team maintains spreadsheets alongside the SaaS tool to track what it cannot
• You have hired a full-time administrator just to manage the platform’s complexity
• Customisation costs now exceed the licence fees
• Users complain that the tool makes simple tasks complicated

If you recognise three or more of these, you are fighting the platform. Building custom means building for your actual workflows, not someone else’s idea of them.

Factor 3: Per-Seat Economics

The question: How does the total cost scale with your user count?

SaaS pricing is designed to extract maximum value per user. At 10 users, it is usually reasonable. At 500 users, it can be devastating.

Do the five-year maths:

Scenario	SaaS (£150/user/month, 200 users)	Custom Build
Year 1	£360,000	£100,000 (build) + £10,000 (hosting)
Year 2	£360,000	£25,000 (maintenance) + £10,000
Year 3	£360,000	£25,000 + £10,000
Year 4	£360,000	£25,000 + £10,000
Year 5	£360,000	£25,000 + £10,000
Total	£1,800,000	£250,000

The custom build costs 14% of the SaaS option over five years. Even if we double the build and maintenance estimates to be conservative, it is still under 30%.

Not every comparison is this dramatic, but the principle holds: per-seat SaaS pricing at enterprise scale is where the economics break down most obviously.

Factor 4: Vendor Lock-In Risk

The question: How painful would it be to leave this vendor?

Some SaaS tools are easy to leave. Your data exports cleanly, alternatives exist, and switching costs are low. Others — Salesforce, SAP, ServiceNow — are deliberately sticky. Your data, workflows, customisations, and institutional knowledge are all embedded in the platform.

Lock-in matters because it erodes your negotiating power over time. In year one, you chose the vendor. By year five, the vendor has chosen your renewal price, and you both know your alternatives are limited.

Building custom eliminates vendor lock-in entirely. You own the code, the data, and the infrastructure. If you want to change agencies, change hosting providers, or bring development in-house, you can. This is a core principle of how we work at LiberateWeb — we build on open standards specifically so clients are never dependent on us.

Factor 5: Strategic Differentiation

The question: Does this tool touch a process that differentiates your business?

If the software supports a commodity process (email, accounting, HR administration), buy SaaS every time. You do not gain competitive advantage by building a custom email client.

If the software supports a differentiating process (your unique sales methodology, proprietary operational workflows, customer-facing tooling), building custom gives you the ability to iterate and optimise in ways that SaaS never will.

The SaaS vendor’s roadmap serves their average customer. Your custom tool’s roadmap serves you.

When to Always Buy

Despite everything above, there are categories where buying SaaS is almost always the right call:

• Communication tools: Slack, Teams, email — the network effects and integration ecosystems are unbeatable
• Accounting and finance: Xero, QuickBooks, Sage — regulated, complex, and not your differentiation
• Basic HR: Payroll, benefits administration — too much regulatory complexity to build
• Office productivity: Google Workspace, Microsoft 365 — commodity, cheap, and universal
• Security tools: Authentication (Okta, Auth0), monitoring, endpoint protection — specialist domain

Do not reinvent these wheels. The cost of building is not worth it, and the risk of getting security or compliance wrong is too high.

When to Seriously Consider Building

• CRM/sales tools where Salesforce costs £100K+/year and you use it as a contact database
• Internal operations platforms where ServiceNow or similar costs £80K+/year for glorified ticket tracking
• Customer portals where your current solution is a bolted-on module from a platform not designed for it
• Reporting dashboards where you are paying £50K+/year for Tableau or similar when you need five specific views
• Workflow automation where you are stitching together Zapier, Power Automate, and custom scripts anyway

The Hybrid Approach

Most enterprises should not go all-in on either approach. The smart strategy:

1. Audit your current stack — know what you are paying and what you are using (we have a guide for that)
2. Categorise each tool as commodity (buy) or differentiating (evaluate for build)
3. Start with one custom replacement — pick the tool with the worst cost-to-value ratio
4. Validate and expand — once you see the cost savings and workflow improvements, evaluate the next candidate

This is not about ideology. It is about spending your technology budget where it generates the most value. Some of that budget should go to SaaS. Some of it should go to custom builds. The proportions depend on your business, and anyone who tells you otherwise is selling something.

What to Do Next

If you suspect your enterprise is overpaying for SaaS tools you barely use, we can help you evaluate the build-vs-buy decision for your specific situation. We will tell you straight where SaaS is the right answer — we have no interest in building things that should not be built. But where custom makes sense, the savings are substantial and the operational improvements are real.