re: At which salary level is an individual “doing well”?

IMO about $200k. This basically allows you to have all of the "normal" american items:

1.) $400k house
2.) Newish Truck
3.) Newish 2nd vehicle
4.) Save 15-20% to retirement
5.) Decent boat
6.) 1-2 Nice vacations a year.
7.) Eat out a couple times a month for dinner
8.) Not have to pinch pennies

Less than that, and you are cutting out likely at least one of those.

This does not include private school. So would need to be more for that.

ETA: I figured I'd get downvoted but I'd like to hear your opinions? I had a down year last year due to Covid but I made almost $200k in 2019 and after retirement savings I by no means felt like a baller with 3 kids.