The income amount would be different in different cities. You can’t just look at income, you have to look at assets and savings too.
Assuming little to no savings, the ability to afford food and shelter changes depending on how many dependents you have.
I think mostly I don’t use a specific number, but more like I know it when I see it. If where you live is in a poor area, and you can only afford food, shelter, and transportation, and you live check to check, then you are poor. Even if you have an extra, let’s say, $3k a year where part goes to savings, part clothing, and part to emergencies, that’s still poverty.
My aunt was poor in her final years, but thank goodness NYC has rent stabilization to help people who have lived in the same apartment a long time, and also help to subsidize rent for the poor. So, she could continue to live in her apartment, in a good area, but otherwise she lived basically check to check on social security, and additionally burned through about $7k of savings a year to afford bare minimum. She didn’t have a cell phone, but she did have an iPad and cable TV. She almost never used any form of transportation. I think being able to live in a nice place that’s relatively safe is such a big deal.
Lots of people where I live are check to check in their retirement, but the check is social security (old age SS) they have Medicare, their house is paid off, and they live in a nice place. They are poor, but the guaranteed income and healthcare takes a lot of the stress away from being poor, and I think that’s a really big deal. Not having to work, living in a nice place, and not having to worry too much about financial ruin if they have a health event.
Some people function like the poor even though they make a decent income. They spend all their money as soon as it comes in, even though they could reasonably be saving some. The poor have no choice in the matter, unlike someone who is earning a middle class income or higher. Being one paycheck away from ruin is cash poor. You can make $10k a week and be this type of poor. I don’t consider that person poor, but I’m frustrated (maybe translate that to judging) he/she is a step away from being poor if he loses his job.
Right now my husband feels poor, because of the lack of money coming in, even though we have a lot of savings. We are in our early 50’s. If we had the same money and were 65 or older, he would feel rich. Poor can be a state of mind and is situational, but at the lowest levels there is objectively poor, where the person is poor no matter how you look at it because there is little to no income or savings or assets.