Musk was the golden boy of the Obama administration. Their role model for the world on how we should all go green or feel ashamed if we don't own an ultra expensive Tesla car. All of this while behind the curtains nothing was being done to combat the growing global warming or the inevitable energy crisis, that awaits us after the petrol runs out.
So all in all this is quite typical. They give people a "discount" on their taxes, Musk does plenty of business, and the only loser is the budget. Meaning all of us.
I believe I heard someone say that the reason government gives these perk is because people need jobs to live. Obviously the government can't employ everyone so they give incentives to business owners to entice people to set up businesses. So though the government lose some potential income, people who do get employed earn money for spending.
Whether that's actually good for everyone would be debatable but I believe America have a lower unemployment rate than my country.