[moogleii]

It's hard to say how much of US defense/aerospace costs are due to..."overcharging" though. Also, it looks like the US had a hand in engine development for the initial experimental versions (P.1127). Costs were shared with West Germany as well (from harrier.org.uk). From the wiki:

By the end of 1958, barely eighteen months after the start of the project, all the main features of the P.1127 were developed with one exception, the reaction control system - this was resolved by April 1959.[6] As the P.1127 had been developed at a time of deep UK defense cuts; Hawker had to seek commercial funding, significant engine development funding came from the U.S.[4][7] Wind tunnel tests conducted by NASA Langley Research Center using a sub-scale model showed acceptable flight characteristics.[4][8]

I'm not sure how nimble and less wasteful NASA is, or even if it would be considered "cheap", but their X43A project costs were about 27 million 1958 British pounds ($230M US in 1997).