When new, American cars were quite expensive in our country, dads 1970 impala ( fully loaded) from lendrum and Hartman was about £2000, about the same as the equivalent jaguar. Once a few years old with heavy depreciation they were a lot of car for a little money. Of course fuel consumption was part of the depreciation curve as running them was more expensive . Dads impala did 16/17 around north London his friends big Zodiac Executive did about 21 and a XJ6 4:2 was again well under 20mpg, so the impala wasn’t that bad.