If you search the classifieds, you’ll find a just few want ads for then, and very very few actually listed for sale.
Safe to say they’re rare, but that rarity probably doesn’t translate to value in this situation. I’d guess a buck apiece. Maybe a little more, but that’s just a guess. The market feels flooded right now, and the economy is poo, so you might have trouble getting that, unless you find the right buyer.