Yes, that could add up. I also have a 2014 Tesla, and in those first few years, Tesla was using sensors of a brand called Baolong. They are part of that system where it can give you a warning that a tire is low, but not specifically which one, because it doesn't display the individual tire pressures. At some point, they switched the sensor system. Maybe that was part of the mid-2016 refresh--can't remember. The new system, with the individual tire readouts, had multiple antennas to read the different wheels, and it used Continental brand sensors, and they are not cross-compatible with the old system.
So that could make sense, if someone put in Continental sensors, thinking "That's what Tesla cars use.", but not realizing they won't work on the older system of your 2014 model.
What dealer? Tesla doesn't use dealerships. Did you buy this car used from a 3rd party car dealership?
And it is possible, but pretty expensive, to do a retrofit of the old cars to change out the antennas and sensors and software to get on the new system with the individual tire pressure readings. And that may be what the $530 price quote is for.