I don’t think that’s true anymore. I routinely find 4K/27” monitors for under $100 on Craigslist, and a 3080-equivalent is still good enough to play most games on med-high settings at 4K and ~90Hz, especially if DLSS is available.
Your hypothetical person has a 3080 but needs to crawl craigslist for a sub-100$ monitor? U guess those people exist, but idk why you'd bother with a 3080 to then buy a low refreh rate, high input latency, probably TN, low color accuracy craigslist runoff.