Compare the same scope, report type, period, and delivery assumptions first. Then ask about the engagement team's experience with your service, partner involvement, evidence requests, communication cadence, and how scope changes are priced. Verify the firm and relevant licensing, and ask about peer review where applicable. Request a clear list of exclusions, including readiness work or extra testing that costs more. Ask how exceptions are discussed before report issuance. The cheapest proposal may fit your needs, but a low fee paired with vague testing, unclear staffing, or an unexplained delivery guarantee deserves more questions.
Related: SOC 2 cost considerations; SOC 2 audit and compliance hub.
Further reading: AICPA SOC resources.