https://www.scientificamerican.com/article/israel-proves-the-desalination-era-is-here/
Israel is the world leader in desal tech.
They have water down to 52 cents per cubic meter as of 2020. That’s less than we pay for city water here in North Texas.
There is 264 gal to 1 meter cube we pay 4.5 for 1000 US gallon so 52c per M^3 = $1.96 per 1K gal. We have septic if we didn’t the city charges another 5.5 per 1K gal to take your waste via sewage system.
Desal is too expensive for agriculture except for very high value crops. There is 1233 cubic meters in an acre foot of water or $641 per acre feet of water. In the desert the evaporation transporation can reach 50+ inches of water per year per square foot. That’s over four feet of water that is lost and be irrigated to replace. That doesn’t include the water needed for the plants cellular respiration or growth which can be two more feet per year. Rice uses 6 or more feet per year there is no way water at $641 per foot can support rice or gay or alfalfa or pretty much any grain corn nope, the not even close rice would be 6*641=$3846 for just the water per acre of rice no way could the harvested grain cover that much water expense.
Desal can be used for backup when needed—it would then be more expensive when used but it is a lot better than running out of water.