46 U.S.C. § 57506

1. (a)A vessel constructed under this subtitle or the Merchant Marine Act, 1936, may not be sold by the Secretary of Transportation for less than the price specified in this section.
2. (b)If the vessel is to be operated in foreign trade, the minimum price is the estimated foreign construction cost (exclusive of national defense features) determined as of the date the construction contract is executed, less depreciation under subsection (d).
3. (c)If the vessel is to be operated in domestic trade, the minimum price is the cost of construction in the United States (exclusive of national defense features), less depreciation under subsection (d).
4. (d)Depreciation under subsections (b) and (c) shall be based on—
   1. (1)a 25-year life for dry-cargo and passenger vessels; and
   2. (2)a 20-year life for tankers and other bulk liquid carrier vessels.