atn #10, RN Polaris, and s1,#33, airline purchasing, are a tad unfair.
Few airlines buy "off the drawing board", ahead of the certification process. When BOAC/BEAC were required to do so, when they were instruments of State policy, much anguish ensued.
USN procurement process for Polaris and its SSBNs were unprecedented successes (4.5 years, ITP to deployment); RN's (5.25 years) followed a largely-blazed trail, with a near-blank cheque: unused contingency funds yielded the savings: these boats were estimated by bloat R.Moore, RN & Nuclear Weapons, Harwood, 2001, P17: Programme Manager: “I hadn’t the faintest idea (of hull build cost) so I took projected cost of Valiant (SSN) and doubled it.”
When the State buys de-bugged Commercial Off the Shelf, daring to settle for 80% of ideal Spec., that often works and we hear nothing about it. Trouble arises (not only, though always, in IT) when Ministers are lured into bespoke. The problem is that, for combat kit, bad guys may already have COTS.