Replacement freehubs are a nightmare in any brand. Shimano have absolutely oodles in each apparently compatible speed range. It's often a similar cost to buy a whole new hub, although that gets expensive if you don't build your own wheels. I fancy replacement freehubs are priced in the knowledge that it's too much hassle for most people to replace the hub.
Also a lot of people will just replace the entire wheel as some value oriented wheels cost a similar amount to a freehub body. It only really becomes economically viable on more expensive wheels once labour is factored in.