The horsepower and torque are bumped but they are bumped through software. That means any M4 owner today can have the same output of the M4 GTS through the aftermarket (and then some) for a fraction of the cost.
The GTS is lighter due to the rear seats being pulled and the carbon fiber pieces. These weight saving measures add up to around 200 pounds but we have to see independent weight test numbers. If a current M4 owner wants to ditch weight off their car they have options that will not cost them another $65k.
What about the suspension and aerodynamics? These parts can also be sourced in the aftermarket. For someone to pay $134,200 for an M4 GTS if seeking a track car when the Viper ACR exists for almost $20k less they must really, really, really, love BMW and have money to burn.
To BimmerBoost, the M4 GTS is not worth the money for what amounts to a standard M4 on steroids. Especially considering it features the exact same turbo engine and anyone can add a solid water/meth injection system to their M3/M4 today for under a grand. With the E92 M3 GTS one could not just take their S65 V8 from 4.0 liters to 4.4 liter as easily as it is to bump power output and add water injection to the M4.
Despite the ludicrous pricing we certainly are glad BMW built this car and is selling it in the United States so BMW performance enthusiasts finally have something to at least cheer for in performance comparisons.