A good reason for a cap of $50,000 on the EV rebate, is that it will stimulate manufacturers to have an option that qualifies. It is not just the purchaser you’re trying to stimulate it is also the manufacturers of the electric vehicles.
Take the Kona EV as an example, IIRC , they are only selling premium trim, and have a price higher than some people were expecting. If there is a federal subsidy for only cars under $50k, I am sure they would find a way to get under it. Cheaper EVs, means more people buy them.
Providing a subsidy on a Jaguar, does not have this effect.
Personally I think there should be three criteria:
1) Fully electric, not hybrid
2) 25Kwh minimum battery size
3) under $50k base price.