If you want to be boring, there were a number of + and - cost variations.
When the number of jets was reduced from 18 to 12, the NAO (bless 'em) calculated that it would produce a saving of £155 m with an associated redction in COCC (Cost of Capital Charge) of £10m....
That's £155 m for six aircraft.
£25.8 m each.
Surely it would have been better taking the six aircraft and selling them on (to India or Oz, perhaps?) or using them for R1 replacements, and even to replace the old BAC One Elevens and Andovers at QinetiQ.
If BAE offered six more for £155 m tomorrow I hope the MoD would bite their ****ing hands off.
If you only save £155 m by cancelling six jets, then cancelling them does not look like a great call, to me.