$18K used to be a good price for buying a BBB. If you don't get a buyer for yours it is because I think nobody wants to be the guy who paid $18K for BBB and then saw PPS announce BBBr for $8 (or $9K) NIB. If there is no BBBr coming from PPS then BBB will be a $20K game again someday, but most people would wait a long time for a possible PPS remake first.
I still wouldn't sell my BBB even for $20K. I have a spare plastic set, spare main plastic ramp, spare small plastic divert ramp, spare lighting decal for under the main plastic ramp, blue and orange rings for the tube ramp, spare green tube dancer, pink tube dancer (and a BBB barstool).