The only way I can read what they wrote to mean that is if they are saying water costs $30-40 a gallon.

Have you never used a garden hose? Do you know that a regular, average hose left running overnight can waste like 5,000 gallons of water? My HOA enforces a rule - you must keep at least two trees per household. Trees need water. Not that much, of course, I shared the overnight hose number just for the sense of measure. Now you do the math - couple of trees, bathrooms, showering, drinking, cooking - that water usage adds up.

Trees don’t grow otherwise in that area? Like if you would stop watering, will they die? Future proof solution could be selling and buying somewhere where climate change won’t hit as hard, eg north, but I guess not everyone can afford that, and cooler regions may not offer sufficient sustenance or infrastructure like schools and jobs.

I mean sure don’t leave a garden hose running overnight. That’s insane. If you leave it running next your house you’ll flood your basement.

You said you had a pool though. That and trying to keep 2 non native trees alive in the desert is probably equivalent to irrigating a large yard.

If you live in what sounds like the desert and you're constantly watering your trees, it might be the case that you've picked non-native species that don't handle heat well. Check out the crime pays but botany doesn't on YouTube, he does a lot of videos about this, people in Texas etc planting English oaks and needing to water them all the time while native species are ignored or cut down because they're "messy".