Show them craigslist printouts. theres always crackheads thinking they can get 2500 dollars for stock mopeds.
Show them itemized lists of prices like
handlebar 25.00
fender 50.00
labor 100.00 an hour for probably 6 hours work.
etc........
even if its that old its highly unlikely the appraisal value would be $0
Tell them you want it repaired perfectly so you can rent it out to people for movie filming purposes.