The pricing model for Dynamics GP 2013 and Dynamics NAV 2013 has changed.
Take a look at the details of the new pricing models in the links below.
Dynamics GP 2013 & NAV 2013 Pricing and Licensing
https://mbs.microsoft.com/partnersource/partneressentials/licensingpolicies/perpetual-licensing.htm
Dynamics GP 2013 & NAV 2013 Licensing Guide
https://mbs.microsoft.com/partnersource/pricing/announcements/MSDNAVGP2013LicensingGuide
Hope this helps.