Best discount to calculate net cost for an item

Summary:

Hi

Our customer derives the selling price by deriving "Actual cost" from costing module or "Market cost" captured in cost list.
Some customer uses actual cost and other customer uses market cost and which cost to be used during pricing is configured in customer account DFF.

Customer-A Account DFF value: Actual cost

Customer-B Account DFF value: Market cost

Markup % or amount is also captured in customer master. It is same for all the items.

Multiple GPOs provides discount for the same item. Eligible discount rules are determined by using customer attributes like customer type, group and etc.

Also, vendor may provide a "