The "highness" of that price depends on what they are providing.
If they were providing a 10ft c/ku dish and c/ku lnbf, mounted on pole with 36" actuator, a diseqc compatible mover, and a HD PVR FTA DVB receiver, then you're getting a HECK of a deal.
In reality, for that price you're probably paying high retail price @ approx $150 for a decent bottom-barrel receiver, maybe another $100 for a dish, another $100 for a motor, another $35 for RG6 - which is about $385. So that's about $400 for the install (2-4 hour depending on where/how it has to be mounted)
Depending on what they're providing, they could easily justify that price. But if you want to get started cheaply, you might consider doing the thing yourself. A decent dish/motor/receiver can be had for well under $300 shipped. It's not that tough, and you've got a whole community of people here to help you. Of course, it could easily take you 4,6,10,or 12+ hours to get your install working. So if your time is valuable, and you don't prefer this sort of "fun", then keep calling around and find someone a bit more reasonably priced for your install.