I think the difference here is that the materials used are cheap and easy to procure. That sounds like maintenance should be straightforward. The difference between producing water locally and shipping/trucking it in is probably huge in places without water pipes. A couple of gallons a day goes a long way. Scale it up a little and now you are irrigating your vegetable garden as well.

The Reverse osmosis cost estimate was based on a 10 year committed Hyflux Desalination commercial contract with the PUB in Singapore (from about 5 years ago, so might be less expensive now, actaully) - so includes maintenance costs.

Regardless - this isn't a scale able solution, but doesn't need to be - should work fantastic for a small family with negligible environmental impact.