I am assuming you mean how much does it cost to configure your system with more RAM, rather than buying the RAM itself from Apple... but for the most part 3rd party RAM is cheaper than Apple. But for the iMacs, MacBooks, and MacBook Pros the price of RAM is very reasonable. For the Mac Pros I would buy RAM yourself, but other than that (and maybe the Mini) I would save time and hassle and buy from Apple. That's what I did. Plus you don't have to keep switching the RAM back and forth every time you send it to Apple.