I don't know what they are worth, I get the impression the rock crawler crowd prefers the SM465 these days because they are tougher.
I've been given a couple of them over the years and at this point have given a couple of them to another bolter. While I don't want to be stupid about the value of stuff most these things cost me very little and I'd rather get them into the hands of someone who will see them used rather than worry about a few bucks.
I have at least three and maybe five of them today, so I don't feel they are in short supply.