Interestingly in the 1970s I seem to recall we required the approval of either the Minister for Aviation or Director of DCA to import aircraft or engines?
Pinky, Checkboard answered the question better than I could. The relative cost of aircraft was much less before the absurdity of product insurance etc. In the early 1960s I was offered the very low time Victor Airtourer demonstrator for £3,800 with a flying school contract. In 1975 a new Embraer Bandeirate cost US$580,000 and extraordinary low export finance costs and a spare PT6A-34 engine was US$90,000. In 1987 I bought a Cessna 150 with 1,200 hours for $12,500 and a Grumman Cougar twin with 1,000 hours for $99,000.
Compare those to todays prices for tired old high time GA aircraft.