My grandparents lived a couple of miles from the city where Grandpa worked, but then when he retired they moved maybe 30 miles out where things were cheaper. I knew other folks whose parents or grandparents retired to Florida to take advantage of a lower cost-of-living and no income tax. That's just what people did - why pay a premium to live near the jobs if you aren't working?
More recently I've read complaints about folks from richer areas (often California) moving to cheaper areas, driving up the cost of living, straining local services, etc. Some of them are retirees, although remote work has added to the issue, leading to "go back to California" sentiment in Portland, Boise, etc. I've heard similar stories about expats driving up rents in Mexico City and Portugal, making those areas unaffordable for locals.
So I've got a healthy 401(k) balance and will be retiring one of these days. What are the rules for where I can retire if I want to move somewhere my dollars will go further? Is it still thought of as OK at all to exploit another area's lower cost-of-living in this way? Does it depend on the degree, like it'd be fine if I move to a nearby suburb that is 10% cheaper but not if I move to Thailand? Does it depend on economic conditions in an area, like how many existing residents are being priced out?