On Amazon you can Pre Order the Nyko Data Bank, which is released on the 9th of June, i posted about it here after CES 2015.
The device lets you add a 3.5″ HDD to your PS4 and whilst i can see the benefits when it comes to price, i am not quite sure i can say the same for speed, here are some details for those interested:
Conveniently upgrade your PlayStation 4 hard-drive space.
The Data Bank for the PlayStation 4 allows for use of any 3.5” hard drive in lieu of the stock 2.5” hard drive.
Simply remove the top cover of the PS4 and the internal drive by removing one screw with the included screw driver.
Then you can snap the Data Bank into place. Once installed the databank allows you to use any standard 3.5″ drive which are less expensive at higher capacities than the 2.5″ drives inherently supported by the PS4.
The unit also includes a front facing LED indicator which illustrates when the PlayStation4 is accessing or saving content from the hard drive.
If you are interested in buying it, you can get it for $39.99 here, however i strongly recommend you watch this video out first: