The people that are most likely to die in a heat wave are least likely to be able to afford $400 for a portable room air conditioner.
But they can afford a $400 window unit?
I'm a baby boomer and got my first window air conditioner in 1992. Lots of us who grew up in the 50's, 60's, and 70's did so without air conditioning and survived. I grew up in NYC. There'd be that one week in late July/early August when the temp would hit 100º and we wished we had one.
My son-in-law's parents grew up in southwest Florida without air conditioning. His mother says leather: shoes, belts, etc., would get moldy in the summer because of the heat and humidity.
I'm in Florida now and know people in this day and age who do not have air conditioning.