For the record…I am driving two 30" Cinema Displays off my work Mac (2015 MacBook Pro). I believe the 2012 MBP can drive three displays plus the internal, but this isn't possible on the 2015 MBP.
I am using two of the Apple DVI Dual Link adapters mentioned above. The displays are shared with my 2009 MacPro 4,1 (updated to 5,1) via a dual link high resolution KVM switch.
The TV and the other dark displays you see are connected directly to my MacPro. They are not shared to the MBP because the MBP can't drive anything more than these two displays and the internal LCD.
One of the things to note about the Apple adapter is that the USB plugs are only for power. Since this is the case, it's not necessary to have those plugged into the computer. My MBP cannot power them anyway and I don't have enough ports. So, those are plugged into those small square iPhone power adapters that Apple used to ship with the iPhone. That was a tip given to me by
@Amethyst1.
The work MBP is there on the white stand at the bottom. I run it in clamshell mode.
Lastly, I am using a DisplayLink adapter to get that smaller display on the far left connected to my MacPro. I only have two video cards installed with three ports so that was necessary. The adapter is dual port (DVI and HDMI) so technically I could add an eighth monitor.
I just don't have the space.
@Frazkat The Apple adapters average around $80-100 on eBay. A price I was willing to pay since I work from home and I wanted my work Mac to drive the displays.