Hold on to your butts, comrades. We're about to get a preview of 2050. I just checked the live data, and the area off the coast of South America that is the index water for ENSO is 9° F above average in places. This is going to be a wild year.
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.