Does anyone know how this works?

[spicynacho]

If a manufacturer lowers their MSRP of a product which is already released who eats the cost on existing inventories? Like when sony dropped the price of the 60 GB PS3 from 600->500. Retailers already had stock, I assume they already paid one wholesale price for those and they are being pushed by the manufacturer to sell it for less than they originally intended to sell it for. Does the manufacturer give the retailer a rebate on their inventory, a credit on their next order, or just let them eat the cost?