$9995 for the wheels, motors, uprights, and control unit. $2000 for a battery. Adds 200# (but 0# unsprung). Reduces 0-60 by .6 of a second. Only works to 120 MPH. Max. of 13% regen and no on-board charging, so you're plugging in every night. Uses the CAN bus to determine throttle position - sounds pretty laggy compared to a dedicated sensor/motor controller.
I'll pass.