I am currently trying to sell two Pocket Dragons myself, and the way I tried to determine their prices was by having a look at eBay (based on that, they aren't really worth more than a couple of dollars, but I guess my two are also not very rare). If that doesn't work, or if you can't find matching auctions to the ones you have + in similar condition, I think you should try to ask over at the
Toy Box & Games Cupboard section. This section is rather for asking about buying&selling advice in general, e.g. if you have an issue with a seller or situation, but over there more people will see it who can potentially help