this is a great idea... but i think it's not logical... would be better to have a text field for each usergroup and set the amount for each specific, so we can very focus on each usergroup...

and logically, this becomes are real mess when you have users with multiple usergroups... is the primary group used for identification, or all usergroups... because if i'm member of the group X, Y and Z, and one of your subscription have rebates for group X and have a higher fee for Y, you will have strange behaviors....