Upgrade Draftsight Professional to Draftsight Premium

Hello, 

I purchased Draftsight Professional this August. I am interested in upgrading to Draftsight Premium. I already paid a full price for the Professional version. Is it possible to get a discount once for upgrading rather than paying a full price? In my opinion the upgrade is an extension to an existing version and an upgrade is not worth paying a full price for a new version.

Could you please provide some information on that topic? Thanks