We have a mobile unit (purchased 15+ years ago) which gets used only when temperatures rise above about 30C.
Today, it will be 38C in the shade, bedrooms will be high 20s and my downstairs living area will be about 20C.
Yes, a bit pricey to run (but no different to putting the heating on when it's very cold) - only you can decide if you fancy being so cool in these extremely hot periods.
These units also dehumidify at the same time as cooling- which makes things that more comfortable.