They don't do pricing per GB, but rather by how many Media Agents (actually talk to backup devices) and iDataAgents (backup target, like filesystem, sql, email, etc) you use.  I can't remember if it's Computer Store or MSU Purchasing, but one of them should know the details of the contract MSU has with Commvault and be able to get you a price list. 

 

Also, I should add that their support is pretty good and we've never had trouble with getting any issues resolved.

 

-Steve