For any forest development road that is constructed or paid for by a purchaser of national forest timber or other forest products, the estimated cost of the road construction, including subsequent design changes, shall be considered to be money received for purposes of the payments required to be made under section
500 of this title. To the extent that the appraised value of road construction determined under this subsection reflects funds contributed by the Secretary of Agriculture to build the road to a higher standard pursuant to subsection (e) of this section, the Secretary shall modify the appraisal of the road construction to exclude the effect of the Federal funds.