You can replace the pads, if the rotors are still good. As a rule of thumb, rotors should be replaced every 2-3 pad replacements. If they aren't worn too much, they can usually be turned and used again ... as long as it remains above the minimum thickness.
1100 sounds like a bit too much.
-Front rotors from BavAuto are 70 dollars a piece, and front pads are 60 for Pagid pads (quite possibly the best aftermarket pads).
-Rear rotors are 60 dolalrs a piece and the pads are 50 dollars.
Therefore, complete brake set is 370 dollars ... and a good independent shop should be able to do it in 2 hours max ... at 90 an hour (which is astronomical), you should still end up below 600 ...
So, what I am suggesting is that you take your car in to a good independent BMW shop, see what they say about the rotors, and if they have to be replaced, order the parts from BavAuto and have them replace it all.
Hope that helps.