You have an M5 but really want the 7-series to take out some older clients (as you are getting older too). Your wife has the tamer 5-series (530, 540) and she doesn't want the M5. Your child is now proven his/her skill at driving and really wants an M3 (not the new one, too new and too much power). So what do you do and satisfy everyone? Take my E36 + cash. I get the M5 and you have money-down on the 7 series. Wife, kid and I all love you.
Just havin' some fun. I am selling my E36 to get the M5. If it doesn't sell then I guess I'll just trade.