On the web you can a couple of posts on blogs about the new BizTalk Server 2013 Licensing and Pricing:
The links to resources presented in this article should be sufficient to answer any question you might have on the new licensing model for BizTalk Server 2013. You can study the pricing and licensing datasheet that is available. In case you still would have questions that you can always contact a local reseller or Microsoft Sales.
Read suggested related topics:
Good article Pricing and Licensing is always a very confusing topic in BizTalk Server
Ken Cenerelli edited Revision 5. Comment: Added See Also links; Added tags
Good read