How do you build a three-year total cost of ownership for dealership software?

The line items people forget

Integration fees charged by the other system, transaction or message volume charges, professional services for configuration changes, additional environments, and the annual uplift compounding across the term.

Model the increase explicitly

An uncapped increase clause is an unknown cost. Ask for the cap in writing and model the term at that cap rather than at today's price.

Include the exit

Final export, transition assistance, overlap with the successor system and internal effort. A product that is cheap to run and expensive to leave has a cost you will eventually pay.

Compare like for like

Normalise proposals to the same term, the same rooftops, the same user counts and the same assumptions before comparing. Providers rarely quote in the same shape by default.

A worked structure

Set up a table with rows for subscription, implementation, migration, hardware, training, integration fees, usage charges, support and taxes, and columns for year one, two, three and total. Apply the contractual increase to each year.

Add an exit row for year three. Complete the same table for each provider using the same assumptions.

The comparison becomes a matter of reading two totals and their drivers.

Sensitivity checks

Test how the totals change if usage is twenty percent higher, if a rooftop is added or if the increase is at the cap. A product with a lower base price but steep usage charges may become more expensive at scale. Note which assumptions drive the result and confirm them with the vendor in writing, so that changes to volume do not produce unexpected invoices.

Common mistakes in cost modeling

Leaving out staff time, using promotional pricing that expires, ignoring taxes and third-party fees, comparing different terms and forgetting the cost of the old system's overlap are typical. Keep the model with the contract and update it at renewal with actual invoices, so that the next decision uses real numbers instead of estimates.

Keeping the model honest

Have someone other than the sponsor check the model, verify each assumption against the quote and add a row for anything the vendor said informally. Update the model with real invoices after six months. Comparing forecast with actual shows where the assumptions were wrong and makes the next model better.