Write down the required business outcome
Begin with workflows, users, locations, integrations and constraints. A proposal that solves a different version of the problem cannot be fairly compared on its headline price.
Normalise the cost categories
Separate recurring licences from implementation, data migration, integration, training, support, internal effort and future changes. Mark omitted costs as unknown, not zero. Record the period used for the comparison.
Expose the assumptions inside each quote
Check who supplies clean data, who owns integrations, how customisations are handled and what constitutes completed delivery. These assumptions can shift work and cost back to your team.
Ask vendors to demonstrate the same scenarios
A common set of realistic scenarios is more informative than unrelated sales demonstrations. Define what evidence would support a claim of fit, and identify which issues require a technical assessment or pilot.
Compare exit and operating responsibilities
Understand data export, support coverage, renewal terms, change requests and what happens if a partner or product is replaced. The ongoing relationship is part of the selection decision.