Rover,
It's a few hundred dollars in bushings but those bushings are pressed into castings/extrusions before they get to Freemont thus we all experience the joy of buying the whole assembly and not the bushings. My upper links are relatively inexpensive to produce but you have to press out the existing link's bushings and press them into my arms to keep from forking over $220 per arm to Tesla to get the bushings.
Lower a-arms $550 each
Upper Links $220 each
Torque Links $150 each (guess on my part)
So you are just shy of $2000 in parts for the rear of the car. As a rule of thumb, labor equals parts so now you're up to $4,000. Adding wheels and tires is a big hit as well. Unlike the configuration option, you are not foregoing 19"ers for the 21s; you are buying 21s outright. Lastly, if you need to tamp down demand, up the price.