Biggles, our dev team is working on a small change which will empower the store module with "Discounts" functionality. Once they finish the development, and release the beta to the test team, I will post high level design. I understand from my conversation with them that they are trying to incorporate following functionality to the Store:

1) Capability to create, market, present, and apply various discount codes - don't know where they plan to implement (at check out page or ??)
2) Capability to create offers and to be able to attach offers at various hierarchial levels
3) Capability to extend matrix based calculations for offers, and discount codes to make sure rules are evaluated before any offer, and or discount/coupon code is appled.

At this time, unfortunately I don't have any idea when they plan to release the beta to test team; once I have any rough date I will post it to this forum.

Meanwhile, they are also playing with creating products with negative costs, exploring option of how this can be leverage - although I highly doubt this approach will succeed.

Sincerely,