I thought the RAF had one dog re-spared just before they sold them, to drawings and cert ? should be to hand.
As for cost, could it be a case of they need it so lets set the prise to milk them.
I remember a Beech sundowner had a new spar fitted aboutn 4-5 years ago (due to corrision on a 1700 hrs airframe) by airtime EGHH for about £ 3k, as part of a CofA issue.
Then again the dog was built strong, lots of easy to get at parts !!! so hours to complete works take longer and thats the main reason mx costs ate high.