Even though I’m not actually the one who said that, I’ll try to explain. Population growth in Florida and Texas has indeed outpaced most of the US in the past five years, but it’s not like that’s the trend among all red states, or that those people are (generally speaking) moving to the cheap, rural parts of those states. They’re moving to Miami, Houston, Austin, Nashville, etc., cities which are all experiencing their own housing shocks because they’re now starting to develop the population
density you’d see in some of the cities you’re probably referring to (NYC, SF, etc.). Those cities in red states probably aren’t any cheaper than living in like Fresno, CA or Utica NY at this point. You can’t say “red states are cheaper” and then point at the influx of people into Southern cities which, in their own right, are very expensive to live in. It’s cheaper to live in a red state when you live in bumfuck nowhere, not the places people actually want to live