Seamew: not really an issue of cost-plus pricing.
R&D/prototype funding 4/52 (Korean War), to be quick, cheap for inshore detection (for RAF Coastal Command) and for CVL escorts: Shackleton and Gannet to do the longer, heavier work. Production order 2/55. RAF deleted the idea, 1956; RN after Sandys Defence Paper, 4/57, by when Colossii were gone (even the Putnam hagiography has "as difficult to manage as a race- horse among camels").