That was actually a good decision.
That's a matter of opinion, Marth. There are factors which support and deny each claim, be it; Idea Good, or Idea Bad.
Fact - It would have been the best high-atmosphere superiority fighter jet on the market for decades, only to be beaten by true combat craft in terms of aerial preformance. It would have only recently been facing a future on the block or on the upgrade. The cost reflects that, what it also reflects, is that we already had customers lined up to buy the thing before the first prototype was even constructed. And if we'd gone with the Mirage engines... would'a cut the cost considerably.
Great plane. Also had applications in anti-satellite weaponry.
As for WWII.
Britian is an island nation. It is fully dependant on external supply lines. The Royal Navy would have faced almost certian demise had they not Canadians to help crew their ships (RCN - Royal Canadian Navy) & RCAF (Royal Canadian Air Force). Screw the Yanks, without Canada the war would have gone in a considerably different direction without.
And the only thing that makes Americas fighting forces enviable... Lift and deployment capability. It's the only thing that keeps the Koreans from galavanting all over the globe like some. Airlift, water lift, you name it.
And the Avro Arrow had applications as an anti-submarine and anti-warship technologies too.
I say... Idea Bad.