That argument didn't hold sway with the hundreds of Javelins, Hunters, Swifts, Sea Vixens, Lightnings and Canberras.
Unfortunately, that was in the 1950s when the UK was spending about 10% of GNP on Defence, compared to 7% in the 1960s.
They were also cheaper to develop and cheaper to build than the generation of aircraft that replaced them.
I've also got it in my head that the USA paid for some of them through MDAP. Can anyone confirm that?
You didn't mention the V-bombers, but I think the USA paid for some of them either directly or indirectly.
Also the UK was desperately short of Dollars after World War II. Hence Austerity and the Export Drive. The Treasury didn't have the Dollars to pay for American aircraft even if they were better and cheaper than what the British aircraft industry could make.
And before anyone says, "Then why did they buy 52 Lockheed Neptunes?" The answer is that they were provided via MDAP and IIRC ordered in the first place because Avro couldn't build Shackletons fast enough.
Although they were built in Canada, rather than the USA, I think that the 400+ Canadair Sabres were paid for through MDAP. Can anyone confirm that?