While replacing the water pump, the thermostat is only another 10 minute's work plus $20 USD for the thermostat.
Sounds like they're trying to charge you "full" flat rate for replacing the thermostat without taking into consideration the large amount of duplicative work.
Bring this to their attention and ask for an appropriate charge for the "additional" work of replacing the thermostat while the pump is out of the way and the cooling system is already open.
FWIW, I did this job for the first time this spring (both pump and thermostat) and the entire job was finished in less that three hours. That included removing the battery, draining the system, replacing the pump and thermostat, and flushing and filling the cooling system. If a hobbyist can do this job in this time span, their experienced mechanics should be able to do it in far less time.
Heck, just print this out, show it to the service advisor, and ask him to explain his estimate. See if he can do so without staring at his feet.
Steve
