1997 Mazda 626 clutch replacement

Drive Train Axles Bearings problem
1997 Mazda 626 6 cyl Manual 180000 miles

Over the last week or so, I have been having trouble when shifting. I can shift fine, but then instead of catching and going faster, it seemed like the engine was revving even more. I honestly thought I was just driving badly, being new to driving a manual. So I wrote it off as nothing and tried to be more careful. Then yesterday, it got considerably worse and finally just stopped going. The car will start, it will go into gear, but then the engine just revs and the car won't actually go. I took it to the shop and the guy said I need a new clutch. He gave me an estimate of $850 for parts and labor. That seems like a LOT. Are they rediculously over charging me?