Daft question....but how much would a stored MK3 cost to buy? (for a preserved railway?)
Depends on the value of scrap metals at the point of sale. That's what drives the price of withdrawn vehicles that have no further use on the regular rail network and any sales to other heritage rail etc would need to be at a higher price than they could be sold for scrap. ROSCOs exist to make a profit at the end of the day, so are unlikely to heavily discount for preservationists.