> Are we the kind of species that would sacrifice the lives of so many of its own just to satisfy the ego of a few billionaires?

yes

Historically speaking we are exactly the kind of species that would sacrifice the lives of many to satisfy the lives of a few.

You could say that about most advancements - they started out being laughed at as foolish wastes of money and time.

Half a trillion dollars is spent every year in advertising to those poor people to buy things. Trillions of dollars were spent on chasing jihadis around the desert for 16 years. There is enough money floating around currently spent on nonsense to achieve both yours and Musk's goals.

And if you do not see the potential for positive externalities created here on Earth by arguably the most ambitious project mankind has ever endeavored to undertake, your aperture on the world is quite narrow.