I don't think its gonna cost a $4000 PC or anywhere close to that. You can get a good enough rig for far less that will run the game at highest settings. All you will need is any of the high end nvidia cards (price range $399-$500) and a processor to match it up (any intel i7 will do ) and you got enough PC power to run the game like its nothing. The most it will cost you is less than 2000$ if you just go with other okay parts.
These were BF3 requirements by the way
OS: Windows 7 64-bit
Processor: Quad-core Intel or AMD CPU
Graphics card: DirectX 11 Nvidia or AMD ATI card, Nvidia GeForce GTX 560 or ATI Radeon 6950.
Graphics card memory: 1 GB
Sound card: DirectX compatible sound card
Hard drive: 15 GB for disc version or 10 GB for digital version
You didn't needed even a gtx560 to run it at ultra, an old 480 did fine.
The thing is PC hardware is far more powerful than consoles but no game ever uses it completely not even BF4
<message edited by freakmike on Friday, August 30, 2013 10:18 AM>