The usual framing is a salary comparison. A full-time technology executive costs a certain amount fully loaded; a fractional arrangement costs a fraction of it; therefore the fractional option saves money.
That framing is true and mostly beside the point, because the companies considering this are not choosing between two CIOs. They are choosing between having executive technology judgement in the room and not having it.
What is actually being compared
Most companies between fifty and five hundred people do not have a technology executive. They have a capable IT manager or a managed service provider handling operations, and the decisions that sit above that level get made by whoever is nearest: the CFO, the COO, the founder, or by default.
Those decisions are the expensive ones. Which platform the company runs on for the next seven years. Whether to build or buy. What a vendor contract should say. Whether a system replacement is necessary or whether the problem is process. What risk to accept and what to fix. Whether the integration plan for an acquisition is realistic.
Getting one of those wrong costs more than several years of advisory fees. That is the comparison.
Where the return actually comes from
Four places, in rough order of how quickly they show up.
Contracts and spend. Renewals negotiated with a current picture of usage, entitlement and alternatives. Duplicate tooling retired. Auto-renewals caught before the notice period closes. This is the fastest and the most measurable, and on its own it frequently covers the fee.
Avoided projects. The system replacement that turned out to be a process problem. The platform migration that was not necessary yet. Saying no to a project competently is worth more than delivering one well, and it is much harder to get credit for.
Risk that does not become an event. Harder to measure, and the honest way to describe it is as reduced probability rather than as saved money. But the range of outcomes on a serious incident at a company this size is wide enough that moving the probability meaningfully is worth real money.
Speed on the commercial path. Client security reviews answered in days instead of weeks. Prequalification packages that no longer disqualify you. Diligence that does not stall. For firms whose growth runs through other people's procurement, this is often the largest item.
What it should cost, structurally
Anything genuinely useful at this level is priced as senior judgement, not as hours of delivery. That means a monthly arrangement with a defined scope and a defined rhythm, not an open-ended retainer that quietly becomes a support contract.
The test of whether it is working is not utilisation. It is whether the decisions being made this quarter are better than the decisions that were being made last year, and whether there is a document you can hand to a board, a lender or a client that did not exist before.
The honest limits
A fractional arrangement is not a substitute for delivery capacity. It does not run your service desk, manage your projects day to day, or replace the people who keep things working. If what you need is execution, this is the wrong purchase.
It also does not work without access. An advisor kept at arm's length from the operating detail produces generic advice, which is worth what it costs.