I'm pretty sure that multiple 14-50's on the same circuit is disallowed by the NEC.
210.23
(C) 40- and 50-Ampere Branch Circuits. A 40- or 50-ampere branch circuit shall be permitted to supply cooking appliances that are fastened in place in any occupancy. In other than dwelling units, such circuits shall be permitted to supply fixed lighting units with heavy-duty lampholders, infrared heating units, or other utilization equipment.
and you might be interested in:
625.40 Electric Vehicle Branch Circuit. Each outlet installed for the purpose of charging electric vehicles shall be supplied by an individual branch circuit. Each circuit shall have no other outlets.
Additionally, the Tesla HPWC or UMC is basically the cheapest option for a fixed-in-place charger(really connector). As the previous poster mentioned, you can install an HPWC on as low as a 15 amp circuit, so that's not a hindrance to getting an HPWC. Also keep in mind you get a 30% tax credit, so that $500 HPWC really only costs you $350. If you instead go down the 14-50 path to install a third-party J1772 or even a UMC, you need a pricey 14-50 outlet($75) plus a hefty and expensive GFCI breaker($150). You would indeed qualify for the 30% credit on the outlet and breaker, so you should compare 225*70% = $157 to your $350 HPWC after-credit price.
There's a table around for what the charge rates are, but you can easily approximate it. Take your circuit amperage(lets say 30, as in a 14-30 dryer outlet) multiply that by 80% because its a continuous load, then multiply that by 240(volts). This comes out to 5760 watts, and you'd divide that by the wh/mile of your vehicle, lets say 260, for a result of 22.15 mi/hr.