There may be a bit more to it then just spending $79 for the upgrade. If your buddy's currently running G3.5 on his computer he'll need to check the requirements for G5.0.

There are a lot of people out there who weren't able to upgrade to G4.0 from G3.X when it came out because of the newer increased computer requirements. The same thing is still true today. Before spending the money to upgrade be sure that your computer meets the necassary requirements!