As a little bit of context re cost, we're about to put one of our locos in for a boiler overhaul in order to get it up to standard for a 10 year ticket. It's a tiny 0-4-0 German built loco. Cost of the boiler overhaul alone is almost £30,000. While I perhaps don't agree with the amount put into a single project, it's easy to see how it could cost so much.