I just bought a demo X3 last week. First thing.. is it going to be a certified pre-owened? If they aren't going to certify it then it is very high. If it certified then I would also start hagling with them about extra options that you want.... Alarm System (About $400)... Universal Garage Door Opener (About $800)... Floor Mats... ect. Then I would start talking with them about extended maintance! Since it was a demo car I would ask them to put the extended maintance on it for the $37,000 (a $1495 option). If you can get any of these things added that would sweeten the deal. Edmunds user car value on it will proboly be right about $37k so you are pretty close.
A BMW that is under warrany and all maintance covered for 6-year/100,000 miles.... what more could you ask for.