Well, if the subsidies and benefits don't make a difference let's stop them now.
BTW, it's much more than just the tax return to buyers. Here is one example
http://money.cnn.com/2013/05/21/news/companies/tesla-windfall/
Zapta, you're clearly an intelligent person. Why would you suggest a company should not take benefits offered to it by the government? A company would be foolish (and acting against the desire of its shareholders) to not accept subsidies where offered. Companies don't operate on moral compasses! (For the record, I support these credits. I support the UK £5,000 plugin grant, even though I am a taxpayer.)
Tesla receive about $7,500 per car. They also receive about $100mn per year in ZEV credits. That is a lot, but if you're concerned about your taxes being misused, then you should focus elsewhere, because it really is a drop in the ocean.
Tesla aren't currently profitable, so it would be foolish to say they would be profitable without the subsidies. However if you look at their Capex spending (which is service centres, superchargers, Fremont expansion, Gigafactory, R&D) you can see why. If you took this away and just looked at it on a car-by-car basis, Tesla make around $20k per car. So $7,500 doesn't affect them, insofar as they would still be profitable.
FWIW, I would not personally consider the Nevada gigafactory incentives to be a taxpayer subsidy, because they are commonly offered by states to attract other companies to build in their area. This is common practice. Nevada is making a bet on a $20bn windfall over 20 years. You can look it at another way: No incentives, no Tesla GF, and also no tax gain/loss. Offered incentives, small area of land lost (sold by private owner no less), possible $20bn tax windfall after 20 years. You can't lose!