Price list
A selling price comes from a cost: a markup on it, a gross margin of it, or a fixed price instead of it. The rule that applies is the most specific one in scope — a contract for this customer and this product beats their price list, which beats the product's rule, which beats its category's, which beats the company default.
Volume rebates
Where a customer earns a discount by reaching an annual volume, each sale is recognised net of what is expected back and the accrual builds as a liability — recognising full revenue all year and taking a large debit on settlement misstates every interim period. The estimate is re-read at each close and the change applies from then on, never backwards.
Add a rule
Dated: a price list is changed rather than edited, so an order quoted last month can still be explained by the rule that governed then. This says what to ask; whether it may be sold at that is the margin floor's question, asked when the order is raised.