You are incorrect. Costs were substantially lower then.
"What Is the Highway Trust Fund?
The Highway Trust Fund (HTF) was created by the Highway Revenue Act of 1956 (Pub. L. 84-627), primarily to ensure a dependable source of financing for the National System of Interstate and Defense Highways and also as the source of funding for the remainder of the Federal-aid Highway Program. Prior to the creation of the HTF, federal financial assistance to support highway programs came from the General Fund of the U.S. Treasury. While federal motor fuel and motor vehicle taxes did exist before the creation of the HTF, the receipts were directed to the General Fund, and there was no relationship between the receipts from these taxes and feder