Diggory Haddoke (in the UK, obviously) claims to be able to rebarrel and restock a classic action for as little as 15K. Basically, a new gun.

https://www.vintageguns.co.uk/gun-services/service-repair

Probably does everything shy of that as well. It would be worth having a proofed new set of barrels for that kind of money from my perspective.