Hi Terry, There is unfortunately no hard and fast rules with second hand prices....a lot depends on desirability, condition, rarity, restored or unrestored...
As a wise fella once said, "something is worth what some silly bugger will pay for it!" Scott Bonnar prices do fluctuate quite a bit judging by what is auctioned on e-bay.
Please do not PM me asking for support. Please post your questions in the appropriate forums, as the replies it may receive may help all members, not just the individual member. Kindest Regards, Darryl