Yeah I’m young, but I get by fine with about 1000-1100/month, minus rare expenses. I think I could pull getting by with 300k if I outright owned a duplex in the midwest and only had to support myself since 300k would give me 10k+ a year or so in income after inflation & taxes and I’d have no house or car payments to spend that 10k on. I’m 26 though, not too young. But that figure is based on the assumption that I only support myself, own my own duplex and rent the other half out to someone, and manage to get my automobiles cheaply by buying and selling them correctly.
There is an entire subject on living cheaply to be free called voluntary simplicity. I can’t remember the name offhand but I’m sure I’ve read books on people getting by fine with a next egg of 200-400k or so. Just as long as you own your own place (preferably a place where you can rent some of it out) and know how to be cheap.