Meon Valley Flyer
You are quite correct that BAe did do the spar mod on one aircraft, and quoted the MoD a price per airframe that approached the level of the national debt of Bolivia.
So the MoD went off and found another type of aircraft to do the job, it is my contention that BAe was of the opinion that the MoD was over a barrel and would pay to have the work done but this backfired on them!
I have no doubt that when the time comes the UK GA industry will find a way to do the spar job at a fraction of the BAe price but I am told that a number of special bolts have to be made and it is financing the manufacture of these bolts that is the sticking point at the moment. Untill there is enough demand for a production run of these parts the total cost of the job is only speculation but I would not want to be footing the bill for the first aircraft spar re-life.