I'm in the corporate aircraft consulting business and have purchased several numbers from others to put on clients aircraft.
Like some have said, it is what the market will bear. Two already in use ones that stick in my mind were $5000 to refinish a glider and a complete delux paint job on a Cessna plus $10,000 for spending money. For a buyer that just spent $50m for a G550, a few bucks for a number is pocket change.
The most for a reserved one I did was for a copy company that wanted their numbers to match the machine models they built. That guy got a $25,000 check for his $10 registration.
So, I guess the short question is who want's it?
Don