i think it's called negotiating, one of the earlier posters said it the best. You would have to be out of your mind to NOT negotiate. I would'nt even consider that a lowball, a lowball would be $35,000 cash for your m3 listed at 50,XXX.
I just bought brand new 2009 E92 M3 which was listed at $74k, and it wasn't the one I even considered buying, the one I was looking at the guy wouldn't come off of more than $2,000 on even after showing him the invoice price, explaining him why I am offering what I was. Went to the next dealership they gave me over 7k off the list.