So you earn 18k, save 5.5k, and live off 12.5k? Do you have any assets, such as paid off home, that would significantly reduce your monthly expenses? Context would be key here.

I mean my living expenses, including rent, utilities, food, transportation, health care, etc, add up to $1.5k per month (or ~18k per year).

As in, I could make $25k (at a level where the tax rate is effectively near-0) and still save > $5k per year.

Is this employer-provided health care? Sounds like you're receiving is subsidized. Living on $18k a year would be rough. Are you splitting an apartment? How much would you be paying if you had kids and needed another bedroom? Again, context is key. For a single person in their 20s, who will have the lowest level of responsibility and statistically the best health situation of their life, it's possible. But for other people, $1.5k/mo in a HCOL would not cut it.

So you don't actually live on 18k per year, and you're certainly not saving 5k/pa on 18k?

It'd be cool to see a deeper breakdown of your expenses, if you wouldn't mind?