2 CFR § 200.404 - Reasonable costs.
A cost is reasonable if it does not exceed an amount that a prudent person would incur under the circumstances prevailing when the decision was made to incur the cost. In determining the reasonableness of a given cost, consideration must be given to the following:
(a) Whether the cost is generally recognized as ordinary and necessary for the recipient's or subrecipient's operation or the proper and efficient performance of the Federal award;
(b) The restraints or requirements imposed by such factors as sound business practices; arm's-length bargaining; Federal, State, local, tribal, and other laws and regulations; and terms and conditions of the Federal award;
(c) Market prices for comparable costs for the geographic area;
(d) Whether the individuals concerned acted with prudence in the circumstances considering their responsibilities to the recipient or subrecipient, its employees, its students or membership (if applicable), the public at large, and the Federal Government; and
(e) Whether the cost represents a deviation from the recipient's or subrecipient's established written policies and procedures for incurring costs.