The prices aren't outrageous. Depending on the part of the country, labor rates vary greatly. We charge $250 to enlarge the seats (with a "dead pilot" system using Serdi-style cutters), $100 to install the guides and $90 to resurface the pair. This is right in line with Bob's prices.
There are some options that can make a much better outcome for a little more money, like 11/32" stems/guides (valves are significantly lighter, and time has proven plenty tough). We install 1/2" OD bronze "fat guides" in the existing "knock outs", avoiding the added need for pressure testing when new guides are installed (exhaust side is exsposed to water).
ProComp heads, "bare", are NOT ready to install the parts and "go". No aftermarket head is really "ready to run". Unless you pay the "extra" for a pre-ported pair, they're usually a bit "scabby" and need at least some polishing. Usually, the imported heads need a bit of port work to make them perform nearly as well as say, Brodix or Dart. Even those, and E-heads, need some touch up when new. They all need upgraded valve grinds, too. Less expensive CNC-ported heads should be avoided as well, as the porting is suspect at best. "CNC" doesn't necessarily mean better, but it does mean once the ports were established, no improvements were made. We prefer to move ahead each time we do a pair.
Jim