Actually it says the desalinated water is too expensive even for farming, it’s only used for heavy industries, so it’s certainly not a solution for the domestic supply of 9 million people.

And don’t confuse moving the capital city with actually relocating Tehran. Tehran’s not going anywhere. What they’re proposing is building a new capital city, but it’ll be the rich and the political and religious elite who move there. The millions of poor and powerless living in Tehran will get left behind. Some will be able to migrate south, but many won’t.

What's unique about Iran that makes it not feasible? Israel makes more than half of its drinking water from desalination.

actually 90% of potable water in israel comes from desalination. in addition, a bunch of desalinated water supplied to jordan and PA.

also 90%+ of waste water is recycled and used for irrigation

Good answer. Makes sense.

I’m convinced my conjecture was wrong.

No issue.

But the number 100 billion was mentioned as the cost of moving the capital.

for farming you recycle waste water