$42k plus the sales tax savings gets you into the $45k range. I honestly don't think you will fetch $45k on this site for an M3 that is about to be out of warranty. I think $42k is a pretty good offer - maybe beat them up for another $1k.
2013 Alpine White / 335xi M-Sport / 3 Pedals
OEM Performance Carbon Trim / Shifter / Ebrake / Pedals
3M Clear Bra