How do I work out the real cost of a SaaS tool?

The price a tool advertises is the smallest part of what it costs you. Around that sticker sit several other costs that never appear on the invoice: the way the price grows, the hours lost to its gaps, the other tools you keep only to prop it up. Working out the real number is how you compare tools, and builds, honestly.

Step by step

1. Start with the fee, then project how it growsBegin with the actual monthly or yearly price you pay today. Then project it forward honestly: does it rise per seat as you hire, or per usage as you grow, and does it tend to increase at renewal. A tool that looks cheap now can cost far more in two years if its pricing scales with your success. Write down not just today's fee but what it realistically becomes as your business grows, because that trajectory is part of the real cost, and a fee that looks small today can quietly become one of your larger recurring costs a couple of years down the line.
2. Add the hours spent working around itEstimate the time your team spends patching what the tool cannot do: the spreadsheets kept beside it, the data copied by hand, the manual steps that exist only because the tool leaves a gap. Put a rough value on those hours. This workaround cost is invisible on the invoice but very real, and for a badly-fitting tool it can dwarf the subscription itself. A tool that is cheap to buy but expensive to work around is not actually cheap. To estimate it, watch how a typical week actually goes: the spreadsheet someone updates by hand because the tool will not, the report stitched together from three exports, the data re-keyed from one system into another. Put even a rough hourly value on that time and the figure often startles people, because these hours are spread thinly enough to feel invisible while adding up to a serious cost across a year. This is frequently the single largest hidden cost of a badly-fitting tool, and the one least likely to appear anywhere near the invoice.
3. Add the cost of tools you keep only to prop it upSome tools do not stand alone; they need other tools around them to be usable. If you keep a second subscription mainly to fill the first one's gaps, or to move data in and out of it, that second cost belongs to the first tool's real total. Trace these propping costs, because a tool that quietly requires two others to function is far more expensive than its own price suggests, and you only see this when you map the dependencies.
4. Add the switching cost of being locked inEstimate what it would take to leave this tool: the difficulty of exporting your data, the retraining, the workflow rebuilt around its absence. You may never pay this cost, but its size measures how trapped you are, and a tool that is very expensive to leave carries a hidden risk premium. A high switching cost also means the vendor can raise prices with little resistance, so lock-in quietly inflates every future fee as well.
5. Total it across years and compare honestlyAdd the projected fees, the workaround hours, the propping tools and the switching risk, then total the picture across a few years rather than one month. This is the real cost, and it is the only fair number to compare against an alternative tool or a custom build. A build's upfront cost can look large against a monthly fee and small against this full, multi-year total. Comparing sticker to sticker misleads; comparing real cost to real cost is how you decide well.
6. Do the same sum for the alternativeA real cost is only useful next to another real cost, so run the same exercise for whatever you are weighing the tool against, whether that is a different subscription or a build. A cheaper-looking rival may carry its own workarounds and lock-in once you add them up, and a build has upkeep and hosting to include alongside its upfront price. The point is to compare like with like: the full multi-year cost of staying, against the full multi-year cost of switching or building, each with its hidden parts counted. Only then can you see which is genuinely cheaper over the life you will actually use it. Many decisions that look obvious on the sticker prices reverse once both sides are costed honestly, which is exactly why doing the fuller sum for both options, rather than one, is what turns a guess into a decision you can stand behind.
7. Keep the estimate rough, but keep it honestA word of reassurance to close: none of this needs the precision of a formal budget, and waiting for perfect figures is its own trap. The workaround hours can be a fair estimate rather than a timesheet; the future pricing can be a reasonable projection rather than a guarantee; the switching cost can be a considered guess. What matters is not decimal accuracy but including the right categories at all, because the error most people make is not mis-estimating a cost but forgetting whole categories of cost exist. A rough total that counts the fee, the growth, the workarounds, the propping tools and the lock-in will beat a precise total that counts only the fee, every time, because it is measuring the right thing. So do the sum quickly and honestly, revisit it if a tool's circumstances change, and trust it to guide the decision even though it is approximate. The goal is not a perfect number; it is a true enough picture of what a tool really costs you, so that when you weigh keeping it against replacing or building, you are comparing reality with reality rather than one visible fee against another.