If you want non-heated, that $30/side is probably pretty accurate.
I used part number 511 68 119 724 on both sides, RealOEM lists it at $79.52/ea. It will fit on either side, but you don't get the DOT-required 'Objects in mirror...' text on the passenger side mirror.
I hooked the heat up separately, since my car was not wired for heated mirrors from the factory. I ran a couple of wires through the door jamb to the defroster switch, so the heat only comes on when I have the rear defroster on. I believe that BMW has them wired so that they are on all the time (when the car is running), but I didn't see any reason to hook them up like that.
It's a heating element, so one wire to +12V and the other to ground and they are good.