Real oem BMW web site list the compressor at 1174.00 so it seems like your guy is pretty close. The job itself is not that bad to do if you can wrench. You would need to have the system evacuated and recharged correctly in order not to damage the system. I can tell you from first hand experience as a former mechanic, that AC work is not cheap and the parts do tend to be pricey. I would still shop the job around. But keep in mind you do want a warranty with such an expensive job. Use someone you trust and who knows what they are doing. Here's the link for real oem...
http://www.realoem.com/bmw/showparts...94&hg=64&fg=50