Which one are you referring to?
The white (later) car is likely a fake. If it’s real then it’s most likely to have been converted by a third-party rather than Brabus themselves. The 700 conversion is largely a piggy back ECU, upgraded turbos and upgraded catalysts. It’s a proper piece of kit. The 700 conversion is rare on other AMG models too, but I can’t remember ever coming across a CLS 700.
The black earlier car is a real Brabus Rocket, which is completely different kettle of fish - and is the top of the line conversion, done at their factory in Bottrop. A big part of the conversion is fitting the modified V12 engine, and so the donor car can be ordered with any engine. Brakes, suspension, wheels, and interior are all upgraded, albeit all done subtly at that time. That is a a couple leagues above a 700.