Copypasta:
I've had numerous questions about selling the original pages for MLP:FIM. This is to let you know that the 4 pages that have already been previewed from the first issue will be going up on Ebay starting Sunday night, and going for a 10 day auction. We will also be listing a few smaller sketches, possibly some prints, so there will be various goodies to choose from!
If you have purchase inquiries, please let me know! The rest of the pages and the 6 original covers will be going on sale after the release of the book!
Go here for his full statement.
