Let's assume someone is selling an 05 Black LS2 6sp GTO.   
KBB Private Party on it is $17,500.   
It has a cam + supporting mods, long tubes, y-pipe, duals etc. 
It has aftermarket tasteful front and rear fascias. 
It has aftermarket 18's (clean, not blingy).   
It has an Ohio rebuilt title.   
What would you pay?