21" Telsa turbine wheels are priced at $6,000 new, but that includes tires, which would be about $1,600 retail, TPMS which is about $200 retail, and mounting and balancing which would be around $100. $6,000 - ($1,600 + $200 + $100) = $4,100, or about $1,025 per wheel.
Going rate for curb rash repair from a reputable wheel repair shop is about $125 per wheel. Assuming all 4 wheels of the first set need repair, that's $500, so the first set is $800 + $500 = $1,300 total for wheels that would look brand new once repaired. $4,100 - $1,300 = $2,800 savings on that wheel set. Your total cost would be $800 wheels + $500 repair + $200 TPMS + $1,600 tires + $100 mount/balance = $3,200.
But, with used wheels, especially the 21"s which are prone to pothole damage, there could be issues. I would have someone look at the wheels before you buy them to make sure they aren't cracked anywhere, and make sure that the runout is within spec (runout comprises several different measurements to ensure the wheel is not bent or out-of-round). If all 4 wheels pass this inspection, then yes, you have a good deal. Don't skip this. Out-of-round, cracked, or bent wheels are not repairable.
Yes, all Model S wheels are interchangeable on all years -- 19"s, 21"s, 2012-2017. However, the 21"s come in two different sets -- a square set where all wheels are 21" x 8.5", and use 245/35R21 tires, and a staggered set where the front wheels are 21" x 8.5" and use 245/35R21 tires, and the rear wheels are 21" x 9" and use 265/35R21 tires. You will need to know whether each of these used sets is square or staggered to purchase the correct tires.
If the wheels meet specs and are undamaged, then I see no reason why the Tesla service center wouldn't install them. They will, however, insist that you use the OEM 21" tires, which can be:
For staggered setup 21"s: Michelin Pilot Sport PS2, Continental Contisport Contact 5P
For square setup 21"s: Michelin Pilot Super Sport, Continental Contisport Contact 5, Continental Extremecontact DW
If you want to use different tires than these, you will need to have a 3rd-party tire shop do it. Also, many service centers will insist you purchase the tires from Tesla, they won't let you bring in your own, even if they're the correct brand and size. You're likely to pay more for those tires to Tesla than to a 3rd-party tire retailer like TireRack.com.
Yes, you can save money here, but you're going to have to do some leg work to get it done right.
