I would say $16-17k.
You guys nuts? I feel like he MIGHT go to $22-23K, but Jesus Christ $16-17K would be grand theft auto... there are no real comparables out there other than the one I linked at 401 Dixie Hyundai. Every other one has over 100K on the clock, which is fine because the N55 is a pretty stout engine... but they're low-to-mid 20s too.
My question was how much a BMW dealer would potentially offer him for it as his alternative to unload the car by Thursday is to go to BMW dealer(s) and have them cut him a cheque. So my "competition" would be a BMW dealer which would take it in on the spot.
Just about any dealer would be willing to take it... it's too old to CPO and almost two generations old, so even a BMW dealer wouldn't want it for retail. It's a straight to wholesale unit, so any dealer he approaches will send photos to their top few wholesalers, take the best number, pack it for a couple of grand for themselves, and push it out the door. There is no benefit to him going to a BMW dealer versus Mickey-Bob down the road.
I would probably offer him $20K if it checked out mechanically. The cosmetics that Dante mentioned are no worries... typical for a BMW of that age