You can gauge whether you're getting ripped based on the fact that most dealerships are now charging between $95 to $100 an hour for labor and I guess if it's going to take them roughly an hour it's about right. You other options are an independant garage ,although they tend to charge $85 to $95 an hour, find a freind who'll do it for a case of beer or learn to do it yourself. Not much else you can do.
I paid $86 for the lower front engine cover (underside piece that attaches to the fenderwells and the underside of the bumper) including installation. What your dealer is telling you doesn't sound too bad.