one would hope the prices come down, but the common "window units" in the US just basically sit in a window.

the kind of window where the bottom half slides up. thats where you set the window unit, on the window sill, and then close the top on it. then it has some filler piece that expands to the sides to close the gaps, but you can stuff anything in there. it releases heat (using a heat pump) outside the window and cycles air from inside the house that it cools.

it can be surprising how effective they are, but one unit typically handles enough air to cool a single room. so shutting doors or hanging fabric helps.

no holes in walls are needed, and the thing plugs into an outlet inside the house.

if i were some kind of guy who had a boat load of cash, i would be filling shipping containers with them and US/EU power adapters, because an entry level, small window unit here is under $200 USD. and oftentimes, one cool room is all you need to make it through a heat wave.

If you have tilt & turn windows your only option is a mini split AC.

If you have other windows, midea has u-shaped window A/C units which may help with some window designs that typical US style window units wouldn't accommodate.

prices do typically drop in colder months, at least in my area (midwest usa). I would suggest being open to traditional window units as well as they’re typically cheaper than the kind you’re describing (and equally effective iirc). You do need to drill a couple holes into the window frame but the holes won’t even be visible when the windows closed.

Idk what landlord/rental rules are like where you live but personally I’d tell a landlord to go fuck themselves if two holes at the bottom of a window was a major issue.