I don't think your models are very expensive.
also 4 days is nothing... sometimes a model is sold after many months... sometimes it isn't even seen.
try to have more patience and make other models.
I know a guy who sells animal models and specializes in those... without the rig he sells them for around $199 - $299 with the rig and animation even reaching $799 - $999 etc... obviously he's been working on it for many years and has a very extensive collection..