"Expenses", in this sense is not "cash out". When you buy a building, you're just moving value from one store to another (cash -> assets). Only the deprecation (something like 5% p.a. for a building) has an impact on profits.
(although, for technology companies, investments often hurt profits more than for more traditional companies, mainly b/c typical tech investments are hard to value accurately and therefore deprecate immediately or faster – self-created IP as one example)
As long as Musk decides to roll all revenues back into operations, investors get nothing. Musk has a reputation as someone who doesn't really care all that much about his investors, this is a move carefully designed to massage that image. Musk still doesn't care about his investors, but throwing a little cash their way keeps their voices from building to a crescendo.
As for what humanity is getting out of the deal, they already got the Model S and X, it's soon going to get the 3.
Let's not be too breathless when we describe the cars that a few hundred thousand of the wealthiest people on the planet have purchased.
Well, you know, I wasn't. The opposite actually.
It might be worth it in the end, but call a spade a spade.
Ultimately, it comes out of the profits of whichever automakers aren't producing enough low-emission cars.
However oil & gas production receives significant subsidies in many (most?) countries around the world, including the US.
In addition, oil used for things like aviation fuel, heating, power generation, and maritime fuels used for shipping, are typically completely tax-free.
Don't investors get a higher-valued company (and thus higher share price)? At the end of the day, capital gains is capital gains, whether it's realized via dividends or share buybacks or not.