I believe I am configuring my price levels in the way you recommended, unless I am misunderstanding you, in which case I apologize.
Here are more details and screenshots, to clarify.
So if a user is a guest or Registered, I want them to see $120.
If a users'group is SCBA Member (which is a subgroup of Registered), I want them to see $90.
If a user's group is Student Member (which is a different subgroup of Registered), I want them to see FREE.
Right now, I have 2 price levels:
$120 (access groups Guest and Registered are checked off (but none of the subgroups under registered):
$90 (Only the Member group is checked off, beneath Registered)
When I try to add a price level for Student, and I don't enter a price, the price level disappears as soon as I click Save.
Am I doing this wrong? Is there a way to accomplish what I want to do?