I am currently working on a really interesting feature for SilverCart: Graduated Prices. Lets say you want to lower the price of a  printer cartridge from 10.99 to 9.99 if someone buys 5 and more cartridges. Just add a new price range for this product and give the price range a price of 9.99 and a quantity of 5. The store will find this price and displays it in the cart if the quantity is matched. You may even restrict this range by a customer category. Lets say you have a customer category for newly registered customers and want to give them a rebate on their first purchase of a printer cartridge. Just add a price range for the certain cartridge and give the price range a price, a quantity of 1 and link it to the customer category for newly registered customers.