Cubase 7 Query

We’re currently running a recording studio with 2 Apple computer systems both running Cubase Advanced Music Production system. We’re in the process of upgrading the software on the one machine from Cubase 6 to Cubase 7.

We’ve just purchased the newer version stand alone for the one system and thus the setup is running Cubase 6 on the one machine and 7 on the other.

I would just like to find out if there is a cheaper alternate solution in updating the old machine as we already own 1 Cubase 7 license?