If all four of them worked 40hrs/wk doing a minimum wage job ($7/hr in S.Korea), it puts them around $59k/yr, which is above the median household income.
I am not sure what the actual job situation in S. Korea is. Perhaps someone that lives there can enlighten us.
The daughter is constantly depicted at someone who is exceptionally talented, although has no paper credentials for the job she does. The family makes multiple comments about good she is at things and how she belongs in the wealthy lifestyle. When everyone is wading through the sewage water (motif for poverty) she sits sort of dry on the toilet just barely above the others (incredible scene imo). She does an excellent job. I think it’s to make a point about the lack of meritocracy even within class or something.
One thing Americans might fall into thinking is that they poor family in the movie is similar to welfare queens in US. Afaik, there isn't enough support for one to live as a welfare queen in S. Korea.
Another different factor is Jeonse. In S. Korean real estate rental market, monthly rent is rare. Most are rented out as Jeonse. With Jeonse, instead of paying monthly rent, a renter will make a lump-sum deposit on a rental space, at anywhere from 50% to 80% of the market value.
This allow a poor family to have relatively secure housing (although it would be undesirable) while having no money for other essentials.
I'm not sure how it affects the poorest families, I imagine that you can stay in a decrepit "villa" on jeonse alone for many years. More often than not, real-estate loses value and it might not be in the landlord's interest to kick you out.
But in recent years there are definitely a lot of lower-income families that bought property and got out of jeonse, since it makes no sense anymore.
I believe that this situations could get better if HR companies weren't thriving everywhere just cutting down any opportunities for the people with stupid assessments, even universities graduates, and letting the experienced and trained personnel that belong to a business make their calls, but this depends on the business willingness.
If a family of four tried to live in Santa Monica on $59k -- they would only have $39k after taxes. You can't rent even a single shitty room for less than $1k per month. That leaves them $500 a month per person. Health care would take at least $58 (the fine if you don't have health care). That leaves you $440 ($14.50 a day) for everything else. It wouldn't be Parasite bad. But it would be awful.
If you just moved to Compton or San Bernardino, it would be fine.
So at that point, maybe its 2 parents and 2 single adults so you cannot combine their income for tax purposes. Maybe each makes $15k which is a very low amount for paying any taxes.
I've been watching K-cinema on/off for a few years, old boy really f'd me up even though I thought I got used things like Bijita Q type J-films. But, if you're looking for what that would look like via a Korean-Californian perspective watch Ms. Purple:
https://www.youtube.com/watch?v=XsYh3MAE0b4
It makes the plight of the Korean immigrant, and ultimate success in LA, all the more poignant. I was a SoCal kid during the LA riots when K-town was burned to the ground and many were left destitute and went bankrupt, now K-town is most of DTLA and has expanded into a lot of Orange County displacing a lot of the Japanese and even some of the mainly Chinese influences.