I live in Scotland, where the winters are long, and at worst we get a couple of weeks a year of a truely horrible heat/humidity combination.
I'm also well travelled, so well used to experiencing the joys of AC in hot countries.
Yet for some reason the thought of buying an AC unit (or even a fan!) has never once crossed my mind!
If I had thought of it though, I would expect the units to be expensive, and installation to be a pretty specialised (and therefore expensive) thing - the number of homes with AC in Scotland could probably be counted on one hand!
It's absolutely fucking horrible just now though, so I might at least look into it...