Cost is relative
The attitude that anyone who can afford a Tesla doesn't need the subsidy is a misnomer.
1. Everyone has an income. All but the very few have a budget beyond which it's not wise to spend. If your budget is 60K then why not go for a Tesla rather than a diesel Merc?
2. The subsidy is to encourage cleaner vehicles. It shouldn't matter where in the price range it it applied, as long as it acts as an incentive.
I took a model S for a test drive and can say it is a truly remarkable car that I would love to own. Can I afford one? If I gave up holidays and social life, I could, but it's not worth it. I've decided to wait for the model 3, which I will be able to afford without changing my life style.
Do I deserve a subsidy, or should I buy a nice diesel instead?