I posted this on the Ubercart forums but haven't gotten any responce so I thought I'd throw it out here as well.

I have found a bunch of discount moduels and I am playing with them to see if any will do what I want but I have not found anything yet. It seems like it should be a very popular feature though.
I am looking for a role based discount but instead of a percentage off list price I want to do a percentage off markup.
For example if my cost is $50 and list is $70 then my markup is $20. Now I can give a tier one customer 10% off markup and a tier two customer 20% off markup.

This would be necessary for me because some products I sell are only a couple percent above my cost. Others are 50% above my cost. For me to maximize discounts to customers while not loosing money it needs to be based off of that markup.
Since we are able to enter the cost and price when adding a product it seems like it should be easy to do but it doesn't seem like it's commonly done.

It would also be nice to be able to give a quantity discount using the same formula.

Any thoughts?