Build vs. Buy: How to Decide When to Commission Custom Software

Most of the build vs buy software debates I sit in on are not really about software. They are about a director who has been told "the system can't do that" for the third quarter in a row, and a finance lead who has just seen the renewal quote. Somebody says "maybe we should just build our own," the room goes quiet, and the conversation ends there because nobody has a way to answer the question that does not sound like a guess.

I want to give you that answer. Not a generic pros-and-cons list, but the sequence I actually walk clients through when they ask whether to license another tool, push their current platform further, or commission something bespoke.

The three options

The framing that causes the most damage is treating this as a binary. In practice there are three paths, and the middle one is where most mid-market companies should end up.

Buy. License an off-the-shelf product for a well-understood, common process. Payroll, accounting, e-signature, email. These are solved problems and you will not out-engineer a vendor with 400 people working on it.

Buy and extend. License a flexible platform and configure it, automate it, and connect it to the rest of your stack. This is where monday.com sits for a lot of my clients. You get vendor-maintained infrastructure plus workflows shaped around how your team actually operates.

Build. Commission software written for your process, owned by you, with no seat count and no vendor roadmap deciding what you can do next.

Retool's 2026 Build vs. Buy report found that 35% of teams have already replaced at least one SaaS product with something custom, and 78% expect to build more internal tools this year. That is a real shift. It is also being oversold. The right conclusion is not "build everything," it is "you now have a third option that used to be too expensive to consider."

The question that decides most build vs buy software calls

Before cost, before timeline, ask this: does this process differentiate us, or does it just need to work?

A process that just needs to work should be bought. Nobody wins a contract because their expense approvals are unusual. If your process is idiosyncratic in a category where everyone else has settled on a standard, the honest read is often that your process is the problem, not the software.

A process that differentiates you is the candidate for a build. One client of mine does short-run industrial fabrication where quoting depends on a pricing logic their estimators built over twenty years. Every quoting tool on the market forced them to simplify it. Simplifying it was the one thing they could not do, because it was the reason customers came to them. That was a build, and it was obvious once we asked the question in those terms.

Two supporting tests I use:

• The workaround audit. Count the spreadsheets, shared inboxes, and manual re-entry steps orbiting your current tool. Three or more usually means the tool is not carrying the process any more.

• The "no" list. Ask your vendor's roadmap team for the three things you have requested most. If the answer has been "not planned" for two years, you are paying a subscription to wait.

  
  

Run the five-year number, not the sticker price

Sticker price comparisons make buying look obvious and building look reckless. Both are distorted.

On the buy side, a subscription is rarely the real cost. Add implementation, integration work, admin time, training, per-seat creep as you hire, and annual uplifts. Published 2026 benchmarks put mid-market SaaS spend somewhere around $1,800 to $3,800 per employee per year across the whole stack, and the average company now runs a few hundred applications, with a large share of licenses sitting unused. For a single platform, plan on total cost landing well above the line item in the contract.

On the build side, the number people forget is not development, it is the years after. Hosting, monitoring, security patching, dependency updates, and the ongoing changes that any live system needs. A build with no maintenance budget attached is not a plan, it is a liability with a launch date.

Here is the shape of the comparison I put in front of clients. Fill it in with your own figures.

When I have run this properly, the five-year totals are often closer than anyone expects. Which is the point. Once cost stops being the deciding factor, you get to decide on fit, ownership, and control instead, which is where the real difference is.

Where seat count changes the math

One pattern worth bringing up, because it comes up constantly at 150 to 800 employees: per-seat pricing punishes breadth.

If forty people need deep functionality, licensing is efficient. If four hundred people need to submit a request, check a status, and approve something, you are buying full seats to deliver a form and a status page. That is the case where a light custom application in front of your existing platform, using its API, pays for itself quickly. You keep the platform of record and stop paying premium seats for read-only participation.

This is a buy-and-extend outcome, not a rip-and-replace. The distinction matters, because "we should build our own" conversations usually start with a legitimate seat-cost complaint and then overshoot into replacing a system that is working fine.

What a well-scoped custom build actually looks like

If you land on build, scope narrowly. The projects that fail are the ones that try to replace an entire platform in one release. The projects that succeed target one process, integrate with what you already run, and ship something people use within a few months.

Signs a build is scoped correctly:

• It solves one process end to end, not five processes partially.

• It reads from and writes to your existing systems rather than becoming a new island of data.

• There is a named internal owner who decides what changes and what waits.

• Maintenance and support are in the budget from day one, not raised after go-live.

• The first release is deliberately small, with a defined follow-up sequence.

I also want a written answer to the exit question before a line of code is written: if this vendor relationship ends, who holds the repository, the credentials, the documentation, and the data? Your answer should be "we do." Anything else is a rental with extra steps.

FAQ

Is custom software still more expensive than SaaS in 2026?
Not automatically. Development timelines and costs have come down meaningfully in the last two years, while SaaS total cost has gone up through seat growth, add-ons, and renewals. The five-year comparison for a focused internal tool is frequently competitive. The one-year comparison usually is not, so if your horizon is twelve months, buy.

How long does a custom build take?
For a well-scoped single-process application integrated with existing systems, a useful first release in roughly two to four months is a reasonable expectation. Anything quoted at twelve-plus months for a first release is a signal that the scope is too broad, not that the work is that hard.

Can we build on top of monday.com instead of replacing it?
Yes, and for most mid-sized companies that is the better answer. Keep monday.com as the system of record, then add a custom application for the part it cannot do well, connected through the API. You get the specialised piece without giving up the platform your team already knows.

What is the most common mistake in a build vs buy decision?
Comparing a subscription price to a development quote. They are different units. Compare five-year total cost of ownership for both, including internal time, and the decision usually makes itself.

Where to go from here

If you are in the middle of this decision, the fastest way to make progress is to write down the one process in question, count the workarounds around it, and price both paths over five years. If the answer is still not obvious after that, it is usually a buy-and-extend situation.

I help operations leaders near Montreal and across Canada work through exactly this, then deliver whichever path the analysis points to, whether that is a better-configured platform or a custom application built for your process. Get in touch and we can look at your case together.