Some people are stuck on that $4-500 range from 10-15 years ago. You need to account for inflation as $400 buys a lot less today especially post covid. The better question would be how much more money you make now vs then and adjust accordingly. $400 is the new $6-700, so if you were good with $400 then, but not $600 now, you need to have a conversation with your employer.
As far as purchasing a 100k car? I was pricing out a Model S Plaid the other day and even with 50k down I still couldn't justify the monthly on it. Now if I could turn that 50k into 1-1.5k/month passive or flip it to 100k then yeah, I'd go for it. For me it's not so much about covering the monthly payment, but more so being a slave to something I don't own outright especially in this economy. Being able to tell my employer to kick rocks at anytime and not having to worry about it >> being tied hostile work environment or being scared of being laid off just to be able to keep pushing a 100k whip.
There a lots of people right now that are gonna bigly fukked if we enter even a mild recession, because they used their first pair of wings to fly into the sun.