Well, they're really good quality so I think their current price is pretty good. If you make them too expensive then they might be priced at what they're worth, but nobody will want to buy them because their personal opinion of what they're worth isn't as much. A good thing to keep in mind is to not just accept pets on your wishlist for currency, as a lot of people just might not have anything to trade in.
But I'd say... maybe around the total worth of a recent rare for a ham, and a rare and a half for a beast alone? The terrariums should probably be a lot less than the animals themselves as well, in my opinion, but they should still cost a bit since they're a special extra thing. The risk here is that some people might just never get one if they're too pricey.
All in all, you can probably charge a rare or two for each creature if you want them to not be free. I really hope they don't cost though, since I don't think I can buy some myself even if they look good. My suggestion is really just to make them pricey enough to be worth making for you, but not so much that recent people can't get one simply because they don't have old pets or some such.