Those prices aren't out of line.
Shaving a head is a pretty straightforward & simple process. That's why that was only $60.
A machinist that's actually good at what they do will command premium prices. You're not paying for a Joe-Bob in his basement with a drill press & belt sander to do it.
There is a LOT that goes into setup. When it comes to cutting larger seats & installing them, you're figuring on cutting angles, etc. Having a cut a few sets of seats, matching them to the valves, & finally installing them, it is not that easy of a job.