[amykhar]

Next question. Look at the code where payments are accepted. In the area where it verifies the transaction and makes the usergroup switch, etc. does it check to see if the received payment equals the subscription amount that you established?

It looks like it does on this line in paypal.php

$cost = unserialize($sub['cost']);

If so, that's your problem. You are going to have to account for the discount.