Sure, they are worth some money. How much will vary..
But they are still selling it on ebay, and the sales of cans
is still legal if not new.. You just can't buy "new" cans
at a store. You could easily get $25+ a can selling them on
ebay. The buyer, and maybe even the seller has to have EPA
tickets.
I've still got a 30 pound jug of the stuff myself. I see two of those
on ebay going for $280+. I remember a few years ago, it was like
liquid gold, with prices on 30 pounds in the $600-800 range I think.
But the demand has seemed to fallen off, and they aren't getting that
kind of money now.
BTW, I much prefer using R-12 in R-12 systems. That's why I keep
what I have, just in case I run into them. I had a Honda Accord that
used R-12, but I don't have it now. It was the last vehicle I had that
used it.
I don't like 134a conversions, because the head pressures run too
high, and you usually have to slightly under charge. Doesn't cool as
well as R-12. And I'm leery of some of the "Freeze 12's", etc..
Some use flammable gasses in the mix. I'd rather use the real deal.
BTW, you will need the "automotive" 609 EPA ticket to deal with
cans. Or at least you did when they sold it in the stores.
Like USAF385, I have the universal 608, but I also have the 609 too.