Jeep Cherokee 2000--a/c compressor locked up?

The mechanic just told me my a/c compressor is locked up and that it needs to be replaced for the car to run. This is going to be about $675. Is this possible? Could I just not run my a/c? I'll sweat a little for that much money. Plus with 75,000 miles on this car, if it is this much, should I sink my money into it? Thanks!