42 CFR § 417.546 - Physicians' services and other Part B supplier services furnished under arrangements.
General principle. The amount paid by an HMO or CMP for physicians' services and other Part B supplier services furnished under arrangements is an allowable cost to the extent it is reasonable. Costs are considered reasonable if they -
(a) Do not exceed those that a prudent and cost-conscious buyer would incur to purchase those services; and
(b) Are comparable to costs incurred for similar services furnished by similar physicians or other suppliers in the same or a similar geographic area.