I'd rather pay $200/rim than $50/rim to a shop that will look after my car/rims, guarantee their work and step up if any problems arise over defects. That's what you get with ACM from what I've rear and heard.
You can pay the cheaper price, of course you can, but down the road it might cost ya.
Current: 2013 Fire Orange E92 M w/orange stitching
Previous: 2011 Jet Black E92 M - 2006 325xi E90 NON-M - 2009 Volkswagen 2.0FSI MK5