Custom Software vs. SaaS Cost: The 3-Year Total Cost of Ownership (TCO) Guide
When should you buy off-the-shelf software and when should you build proprietary systems? An audited financial model comparing the "per-seat SaaS tax" against owned custom software assets.
Building custom software becomes financially superior to renting SaaS when a company has 15 or more users on specialized workflows. Over a 3-year horizon, renting a 25-user vertical SaaS stack at £120/seat/month costs over £108,000 in subscription fees and connector add-ons with zero residual equity. In contrast, engineering a bespoke system in Next.js 15 and PostgreSQL costs £22,000 to £35,000 upfront with £80–£150/month in cloud hosting—saving upwards of £65,000 while creating a proprietary balance sheet asset.
1. 3-Year TCO Comparison Table: 25-User Team Scenario
Consider a UK business consultancy or agency with 25 employees operating on vertical management and workflow software:
| Cost Component | Renting Commercial SaaS | LookADev Bespoke Build | Variance / Savings |
|---|---|---|---|
| Initial Setup & Onboarding | £4,500 (vendor onboarding fee & consultants) | £26,000 (fixed-price complete platform build) | -£21,500 upfront |
| Year 1 Subscription & Hosting | £36,000 (25 seats @ £120/seat/mo) | £1,200 (Cloud hosting @ £100/mo) | +£34,800 saved in Year 1 |
| Year 2 (With 10% SaaS Price Hike) | £39,600 (Vendor price increase + tier add-ons) | £1,500 (Hosting + minor maintenance) | +£38,100 saved in Year 2 |
| Year 3 (Team grows to 30 seats) | £47,520 (30 seats @ increased rate) | £1,800 (Zero per-user charge) | +£45,720 saved in Year 3 |
| 3-Year Total Cost | £127,620 (Rented) | £30,500 (Owned Asset) | +£97,120 NET SAVINGS |
*Break-even point reached at Month 10. By Month 36, the business has saved £97,120 while establishing an internal software system tailored to its exact workflows.
2. The Build vs. Buy Decision Matrix
LookADev never advises building custom software for generic problems. Use this framework to make the right capital allocation decision:
- Commodity infrastructure: Email (Google Workspace / Office 365), chat (Slack).
- Statutory accounting: Tax compliance, payroll, and bookkeeping (Xero / QuickBooks).
- Early validation: When testing a brand-new service with fewer than 5 users.
- Standard generic functions: Where your process does not provide any competitive differentiation.
- Core operational engine: How you deliver your service and create client value.
- High-seat penalty: When paying £100+/user/month punishes you for hiring staff.
- Proprietary client portals: When you need a branded, self-service client experience.
- Spreadsheet replacement: When multi-tab workbooks contain sensitive pricing logic.
- AI and automated pipelines: When you need real-time data sync across APIs without third-party connector limits.
3. The "Per-Seat Tax": How SaaS Punishes Company Growth
Traditional SaaS pricing models are designed around extractive growth: as your company scales from 15 to 50 employees, your monthly software costs multiply fourfold, even though the vendor's cost to serve you remains virtually zero.
Worse, companies begin rationing software licenses to save budget—forcing junior staff to share accounts, restricting contractor visibility, and fragmenting communication back into email and WhatsApp.
Every platform we architect is 100% owned by your business. Whether you have 10 employees or 2,000, your database hosting on PostgreSQL remains under £150/month. You are never penalized for growing your team.
4. Corporate Equity: Rented Expense vs. Balance Sheet Asset
When private equity buyers or strategic acquirers evaluate a mid-market services business, they inspect operational defensibility:
Appears fragile and commoditized. If your operations depend entirely on third-party SaaS and brittle Excel files, there is zero proprietary technology asset. You command lower EBITDA exit multiples.
Commands premium valuation. Proprietary software, automated client onboarding, and bespoke data pipelines prove high operational efficiency, low overhead, and high customer retention.
Frequently Asked Questions
When is building custom software cheaper than subscribing to SaaS?
Custom software is typically cheaper than SaaS when your team has 15 or more users on specialized commercial software, when vendors charge steep per-seat fees that penalize company headcount growth, or when you require custom workflows that off-the-shelf software cannot deliver without expensive workarounds.
What is the typical break-even point for custom business software?
For a mid-sized UK business with 20–35 users, the break-even point between renting an enterprise SaaS stack (£2,500–£4,000/month) and commissioning a bespoke Next.js platform (£22,000–£32,000 one-time) is typically reached within 10 to 14 months.
What about maintenance and hosting costs for custom software?
Modern serverless architecture on platforms like Vercel, Supabase, and AWS costs between £40 and £150 per month for typical SME workloads. Maintenance is minimal because the system is built strictly to your operational requirements without unnecessary third-party bloat.
How does owning custom software affect company valuation?
Renting SaaS is a pure operating expense with zero residual value. Custom software, proprietary databases, and automated workflows are intellectual property (IP) that sit on your balance sheet, increasing valuation multiples during private equity investment or company sale.
Calculate Your 3-Year Software TCO with LookADev
Are you paying tens of thousands of pounds in per-seat software licenses every year? Book a 48h Systems Diagnostic with Lucas Martins to model your build vs. buy economics and map a fixed-price bespoke solution.