Ooh, I LOVE fashion star fillies. If you do decide to sell, I'd be interested in buying a few
Do they have their accesories?
That can really increase their value if they do. I've seen people go crazy over Jasmine's anklets or anything related to Janis. It varies from filly to filly.
I'm not the best with price checks... but have you checked eBay recently? That might help you. There's also a few auctions ending tonight; so I would take a look and see what the winning bid was.
Sorry that I'm not much help, and I hope someone here can better answer your question