[sgerenser]

Mississippi, despite its much lower per capita income than California, has a much higher percentage of housing units with air conditioning (93% vs 72%). AC is now so inexpensive that whether or not a house has AC is mostly about average summer temperatures not income.

[FullMetalBitch]

Average price of AC instalation in Spain goes from 550€ to 5000€ depending on what kind of instalation, equipment and units. Average wage is between around 1300€ net per month.

In Spain it's not cheap.

Edit. And also local towns have rules, I can't just install one that have a device on the outer wall/window and I own the whole house, in the flats you depende on the community to decide.