There is a competition called the 24 hours of lemons, where the car has to cost $500 or less outside of safety equipment. Getting a car for that price is near impossible unless it’s totally crashed out but when I was young $500 specials would run for years without much issue. Car costs are nuts these days.
A private sale $500 car in the US midwest would be expected to run reliably for a few years back in the early 90s.
I think it was up to $1,000 by 2000 in the same area, so the auther is probably in their 50s or older and doesn’t understand inflation.