How much does it cost to prepare for a Maturity Level X assessment?
It depends (noticing a trend here?). Your organization will need to collect objective evidence that its program meets the objectives defined in the CMMC Model for the Maturity Level certification you desire. If you can do this in-house, the costs can be low. If you need to bring in outside assistance, then the cost will increase.
The C3PAO will appoint a Lead Assessor who will review the objective evidence you have collected, in an effort to determine if the assessment will likely proceed efficiently. If they feel that your objective evidence is not sufficient to proceed, they will likely reschedule your assessment. If the objective evidence is not sufficient to proceed, the C3PAO will not be able to give you any kind of feedback on how to address the deficiencies. That is considered consulting advice and it is against the CMMC-AB’s Code of Conduct for a C3PAO to offer consulting advice to an organization it is assessing.