I purchased the 500GB 7200rpm Hitachi Travelstar. I picked it up for $60 a few weeks ago via slickdeals.
It's the same exact drive that everyone recommends using in the MBPs. It's whisper quite and uses very little power. And I believe it's the exact same drive that Apple charges $300 to upgrade to. If retail customers can pick one up for a fifth of that price, then you would have to be silly to think that it costs them more than $40 per drive for Apple when bought in bulk and in large quanties directly from the manufacturer.
I just looked on the Apple.ca store and the upgrade drive is a 500 GB 5400 rpm drive for $165. It' still a collossal rip-off, but the fact that it's a 5400 rpm drive tells me that Apple prefers them due to both power consumption and heat production advantages over the faster 7200 rpm drives.
Some mark up is understandable. But customers do have the right to complain when the markup so grossly and significantly exceeds what they can purchase it for from other retailers.
Sure. Or you could buy the lower-specced model and upgrade after the fact. Apple encourages memory and storage upgrades by detailing how to perform them in the product manual.