Some prices are in the ravnheart Database (http://ravnheart.com/windstone/index.php) but mostly the grey bengals. I don´t think there is currently another “official” place to look for these prices.
I saved some of the “normal” bengals:
sitting chick #4: $355
sitting chick #8: $183
sitting chick #9: $232
I also have some of the silver bengal prices. Let me know if you need them 🙂
Recently Pam created a sticky called “Windstone Appraisals” and put it at the top of the Flea Market “Buy/Sell” page. There are some good search tips that were added following that post – one of them should help you find the original prices (I think it is by JoliesDragons).