If they have a good, documented history these high prices can be justified. There seem to be many cars that are modified professionally and it’s a good way in for the OP without the primary costs.
It’s still the case you don’t get a good return on modding but it’s softened when the hard core that do everything themselves have been joined by those happy to pay others to help. It’s always been the case of course but now the humble mx is seen as worthy of attention …