I've sat on both sides of this conversation more times than I can count: a business owner staring at a SaaS quote wondering if they should just build it themselves, or a team three months into a custom build wondering if they should have just bought the tool. The build vs buy software decision gets treated like a budget question, but it's actually a strategy question, and getting the framing wrong is what causes the regret.
Here's the framing that's worked for every client I've walked through this: is the workflow in question your competitive edge, or is it plumbing. Plumbing is what every business in your category needs and none of them win or lose because of it, accounting, HR, generic CRM, email. Your edge is the thing customers notice, the thing a competitor can't easily copy, the process that actually differentiates how you serve them.
Get that one distinction right and the rest of the decision mostly falls out of it. Get it wrong, and you'll either overpay in flexibility you didn't need or underbuild the one thing that was supposed to set you apart.
Buy the Plumbing
If the workflow is plumbing, buy it, almost without exception. Payroll, accounting, standard CRM, email marketing, basic inventory tracking, these are solved problems with mature vendors who've spent years hardening edge cases you haven't even thought of yet. Building your own version means re-discovering, slowly and expensively, every edge case the SaaS vendor already handled: tax rule changes, security patches, multi-currency quirks, compliance updates.
The hidden cost people forget on the buy side is customization creep. A SaaS tool looks like it fits 90% of your process on the demo call, so you buy it. Then over the next year you customize it, plugins, workarounds, integrations, until you've spent as much on customization as a custom build would have cost, except now you're also paying a monthly license and you're locked into someone else's roadmap. The rule I give clients: if you're customizing a SaaS tool past roughly 20% of its core workflow, stop and re-run this decision, you may have picked the wrong side.
Build the Edge
If the workflow is genuinely your competitive edge, building custom is usually right, even though it's more expensive up front. The reasoning: if it's the thing that differentiates you, you want full control over how it evolves, and you don't want your differentiator to be identical to every competitor using the same SaaS platform.
But "build the edge" comes with a cost people underestimate: maintenance is a permanent salary line, not a one-time project cost. A custom system doesn't stop needing attention after launch. Someone has to keep it running, patch security issues, adapt it as your business changes. That's an ongoing headcount cost, not a sunk project fee.
The Hidden Costs Both Sides Forget
| What you see upfront | What gets forgotten | |
|---|---|---|
| Buy (SaaS) | Monthly subscription fee | Customization work, integration costs, data lock-in if you switch vendors later |
| Build (Custom) | Development project cost | Ongoing maintenance salary, hosting/infra, the opportunity cost of engineering time not spent on your actual differentiator |
Neither side is free after the invoice. The question is which hidden cost you'd rather manage.
A Worked Example in Rupiah
Say a multifinance company is deciding whether to buy a generic loan-collections SaaS tool or build a custom collections system.
Buy path: A collections SaaS runs roughly Rp15 million/month for a mid-size portfolio. Over three years that's about Rp540 million. But this company's collection process has unusual field-visit logistics that the SaaS doesn't support well, so they end up paying an implementation partner roughly Rp200 million over the same period for workarounds and integrations. Total three-year cost: about Rp740 million, and they still don't fully control the workflow that differentiates their collection recovery rate from competitors.
Build path: A custom collections system, similar in scope to what I've helped build for clients in this exact space, runs roughly Rp450 million to build over four to six months. Add a maintenance cost of one dedicated engineer at roughly Rp15 million/month, about Rp540 million over three years. Total three-year cost: about Rp990 million, higher upfront, but they own the system outright, iterate on it as fast as they need, and it becomes a real point of differentiation in recovery rates rather than a shared tool every competitor also has access to.
In this case, because collections logistics and recovery strategy actually were this company's competitive edge, not plumbing, the higher build cost was the right call. I walked through a very similar real case in A Multifinance Firm Digitized Collections and Cut Losses, including what the recovery-rate improvement looked like after the system went live.
The math flips completely if the workflow in question is generic, say, standard expense reporting. There, the SaaS option wins clearly because there's no differentiation to protect and the customization cost stays low.
Questions to Ask Before You Decide
- Would a competitor lose customers if they didn't have this capability? If no, it's plumbing, buy it.
- Are we customizing more than 20% of the SaaS tool's core workflow? If yes, re-run this decision.
- Do we have (or can we hire) someone to own this long-term if we build it? If not, building creates a bigger risk than any SaaS lock-in.
- What's our realistic three-year cost on both sides, including the hidden costs above? Most people only compare year-one costs, which biases toward buying even when building is cheaper over time.
If you're earlier in the process and haven't even mapped which of your systems are edge versus plumbing yet, Digital Transformation for Small Business: Where to Start is a good prerequisite read.
Takeaway: Let the Edge Test Decide, Not the Invoice
Don't start this decision by comparing prices. Start by asking whether the workflow is your competitive edge or plumbing, that answer determines which hidden costs you'll actually be signing up for. Buy the plumbing without guilt. Build the edge with eyes open about the ongoing maintenance cost. If you're not sure which category a specific system falls into, that's exactly the kind of assessment worth getting an outside technical opinion on before you commit budget, which is something I help companies work through at ervandra.com/partner.