I see the OP's point that fewer people will buy without the tax credit, and agree that is true to some extent - though we don't have the data to say just how much.
However, I have a few other issues:
1. I don't believe the presumptive "intent" of the tax credit is correct. While hoped-for competitive pricing after the tax credit expires was definitely a factor in justifying passing the tax credit, if you look at the number and the amount it is clear that was not the intent. The number is not large enough for a full run of a mass-market car below costs, and the $7,500 amount was very specifically chosen as an NPV offset of the $12k in subsidies that the GAO estimated (at Bush's request in 2008 for this purpose) the average gas car got over their lifetime. It was to level the subsidy market to make prices more comparable; not to get them to drop after the subsidy is removed. There are indeed linked effects between the two, but the difference in intent is large enough to change the conclusions.
2. Hybrid prices did not drop when their subsidies were removed. I have read studies on this, and in fact the presumption in the studies was that this was a good result. Prices dropping would have meant that the company was just pocketing profit at the government's expense with no extra sales of the desired technology. The feds do not expect EV makers to drop prices by $7500 when the tax credits expire. The purpose is not to get on-the-edge buyers to be able to afford one either. It's to drive buying behavior of a technology that pays off for the US in economic and strategic terms - the expectation is that the vast majority of new car (especially new tech) buyers can afford it with or without the tax credit, but the incentive nudges them towards a car that most would otherwise avoid in the early days because of standard new-tech fears. After the cars have been around for a while, people are willing to pay more for that no-longer-scary tech, which is why (in general terms; the details are very complicated) automakers can keep selling at the same price despite the tax credit going away.
3. As pointed out by others, different countries have different incentives. So do different states. EV makers aren't adjusting their prices as these other incentives come and go. The feds don't expect it in this case.
4. Automakers don't just set a random price for a car. It has to be above their per-car costs, in fact enough higher that all fixed development costs ($1B per car is a typical industry number; this is why volume is so important to automakers) will be paid for over the car's run. It is a complicated profit-maximization calculation; higher prices mean greater margins but fewer cars sold, so there is some variation but not a lot - especially when competitors are doing something similar which greatly increases price elasticity. Ford was able to greatly undercut other cars at the time not just by fiat, but by greatly reducing production costs (which was no mean feat; it took him more than one try to be able to pull it off).
5. Given #4, prices can't dramatically change mid-stream of a product. They often do go down slightly as the car ages and becomes less competitive, or as per-car costs drop (which may be the case with batteries). Although adding content is another method that Tesla seems to favor.
In sum, I agree with Skotty - the tax credit does help drive down the price of EVs, but automakers won't be able to (and are not expected to) just drop prices when it goes away. Instead, they will be able to sell more cars in the early days when most people might otherwise buy a "safer" gas car; and then use the profits and price reductions (from volume, institutional knowledge, revs of new tech, etc) from the larger-than-otherwise run of an early car to be able to produce another, cheaper line of cars in the future.