Really its a terrible decision, for everyone involved.

PS3 hardware in the PS4 which is the cheapest route outside of streaming will cost at least 200$.

Sony can take the loss and accumulate about 2 billion in losses from this alone i.e 8.4 mill * 200 = 1.6 billion.

Sell the PS4 at 600$, get destroyed by the competition in exactly the same way as the PS3, and consumers have to pay more for the system.

Or they can weaken the PS4 by using the cell in it, effectively spending making a console that cost 200$ that would probably be at parity with Wii U in performance at best, much below it at worse. Competing with a 500$ console, with much more power. 

Every scenario is bad, its really an issue of purposely using exotic architectures in the past.

what was so cheap about Wind Waker HD?

Re-recording all music with a full orchestra

Changing the aspect ratio for the game from 4:3 to 16:9 (and not by just stretching the picture or adding black bars)

Updating all the graphics

adding content into the game such as Miiverse functionality (for posting pictures, sending pictures in game in bottles for people to find and leave hints), adding a HUD on the second screen for quick map and item access

Adding off tv play

 Now what is TLOU going to do for their remake

Update graphics

Yeah, the parallels are uncanny.