Their 20" set-up, with wheels and tires starts at $3700 for the pre-refresh, though is much higher for the refresh. Those are pretty fancy rims though.
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I am assuming that there are significant issues with developing thinner rims in order to make them durable enough to handle the same stresses and a thicker 19" rim. Looking at their site, their current price point for a complete set of 19's, with tires, is about $3,100 to $3,300. Again, pre-refresh. Since the refresh has staggered wheels, I might expect a bit higher of a price, but perhaps not too much of a difference from what they have now
Tesla Model S 19 inch Aftermarket Wheel and Tire Packages. 19 inch Tesla TST, TSS, and Forged Wheels for Tesla Model S by T Sportline. Shop turbine style wheels, arachnid style wheels, and forged aftermarket Tesla wheels for your Tesla Model S.
tsportline.com