I'm not going to try to justify the spending, or the mindset generally.
If your friends are each earning say $150k (2x $150k = $300k) then they may well be susceptible to job less, etc.
But I'd say at some point, probably around US$250k or so, you really do start becoming near-invincible as far as your work goes. Save for health problems, for which you can get insurance.
When I think of fairly high earning jobs, like surgeon, CEO, trial lawyer, specialist physician etc - they all have very good job security. There's always going to be a demand for surgeons. There's little intra-clan competition, and no competition on price. There's no transparency. They basically operate a cartel. Likewise, CEOs operate in their little bubble with little to no accountability.
So it may well be right to say that beyond a certain point, your income is likely assured, barring physical incapacity or malpractice.