I saw on the news that consoles are generally sold at a loss, and make most of its money when people buy a few games, controllers, DLC, and subscriptions. Console makers may lose more money if they use larger and more expensive hard drives, but still keeping the price below $400 or $500.
Hard drive makers have to pay for the metal, magnets, chips, and plastic to make the hard drive. They also need to pay patent fees to the rightful owners of the patents who created the hard drive's firmware/driver software, and patents for physical parts like screws, chips, motors, and materials which are needed to make the hard drives, so hard drives may still cost a lot even after bulk buying.
2TB and larger hard drives may also require slightly more materials, and patent fees if it uses new tech patents to make them.
Bulk buying too many more expensive hard drives is also risky. Sony could be stuck with a lot of unsold more expensive PS4s with 2TB hard drives if the PS4 cost more, and don't have enough good games in the future which most average gamers wants to play.
Average buyers could end up mostly buying the cheaper Xbox One 500 GB version which also supports USB external expandable storage where users can hook up a external USB hard drive up to 16TB in size or a faster external USB 3.0 SSD drive to the Xbox One USB 3.0 port when users run low on internal drive space. The Xbox One supports an external hard drive which is up to 16TB in size according to
N4G.
I think Sony and Microsoft may also be getting a good discount by buying a lot of the world's remaining 500 GB hard drives since almost no computer system builder or hobbyist computer bulder will buy a 500 GB hard drives in 2016 to install in laptops, desktop PCs, and DVR devices except for people on a very
tight budget where they can't afford a 1TB or larger hard drive. A lot of hard drive companies maybe selling their remaining stock of 500GB hard drives at a loss or below the actual cost it is to make them before almost no company buys the hard drive, and the drives end up being too small to use for most tasks like smaller sized 128MB USB Flash drives from the early days of flash drives.
I bet, not many companies are still actively making, and selling 500 GB hard drives these days, and rather recover their warehouse space to store 1 TB, 2TB, and larger sized hard drives which are easier to sell.