Earlier quoted context omitted.
More electric vehicles will get on the road when there is a realistic economic rationale to buy them. Without the subsidy, an $80,000 car that can only go 200 miles is a lot less appealing.
Hence they are subsidized. People with a bit of forward vision realize that without an economic incentive today, there may not be an economic rationale tomorrow, since the technology will not miraculously develop itself.
The alternative would be making petrol-car drivers paying for the actual costs of cars including healthcare for diseases related with pollution, possibly at any level of the production chain and so on.
Hidden costs are often cut away and offloaded on community (I couldn't find anything specifically related with cars (didn't have time to look for), but for comparison here's a short video that shows the real costs of meat https://www.youtube.com/watch?v=uZDsSnpYZrw). Incentives make it a little bit more explicit. While it may be true claiming that Teslas cost would be higher without incentives, for sure Ford's car would be way more expensive if everything had been taken into account.