> I can not imagine what one could possibly need $300,000 per year for unless an apartment costs like $200,000 per year.

Being able to afford unpredictable expenses and not have it bankrupt you. In the US, that would include healthcare. Everywhere in the world, that would be useful if you were laid off.

To build an emergency fund, you just need an income that's a bit higher than your expenses. If you earn $60,000 after tax per year, and spend $50,000 per year, you have a decent $10,000 emergency fund after one year and a massive $100,000 emergency fund after a decade. You don't need $300,000 per year to save.