Premium plugins and pro-sites

As far as I understand it, the way pro-sites works with premium plugins, is that the levels are a heirachy. i.e. If I assign a premium plug in (call it PP1) to Pro-level-1, then PP1 is available to pro-level-2. Did I get that right?

So if I have two different plugins PP1 and PP2 which both have an equal value and do a different task I can't set it up so that PP1 is available for $5 or PP2 is available for $5 or both are available for say $7.50? Am I right? Is there a way of achieving this scenario with the exsting functionality, or perhaps a little bit of tweaking?