Is $800 a ripoff to fix an air conditioning sytem?

Is 800$ a ripoff to fix an air conditioning system that "has a leak" according to the mechanic. The car's AC still blows out air, but it is always hot. I lived with no A.C. For about two year, but since this summer has been very hot, I decided I had to get my AC fixed and get the cold air pumping. My Car is an 08 Ford Taurus and the mechanic claims that, to get the A.C. Working since the "leak" is pretty extreme, it would cost 400 for the parts and 400 for the service. Does this seem like a legit quote to get my AC back up and running or am I getting ripped off?