@bwilliams - There was a change in the TPMS sensor which Tesla used starting in around Sept 2014, so I'd be certain that the ones your get at compatible if your 2014 MS is prior to that change over. Any easy way to tell is that prior to this change you only got a single low pressure alert versus after the change the system now had the ability to display all the individual pressures.
I'm suspicious that yours might as I know others have reported that Tesla would want to change the whole system over when people needed one of the original Baolong supplied TPMS. The price you were quoted sounds like this case, which then also includes changing the TPMS receiving unit in the car along with all four sensors.
Here's a link to a good reference thread on TMS. Look down to about the 4th entry. There's a very helpful post that will give you the approximate VIN for the switchover date plus the original supplier part number references.
How to find the tire pressure reading on a 2014 Model S 60
I'd be cautious about the guidance that any generic 433MHz TPMS will work. I'm not sure that's correct if your 2014 MS is before that changeover date from the Baolong sensor to the Continental supplies TPMS.