What's pessimistic about them? They're hundred billion dollar scale problems, surely one could recover some of that. Currently desalination plants are even more expensive, and they don't do anything with the waste product. And breeding isn't very expensive at all, though with dust mites it's tricky because they're quite small and transparent to visible light.
The ideas aren't pessimistic; you're just preaching to the wrong choir. Those aren't startup ideas, those are huge problems that need research and huge amounts of capital. People also need cars that don't use gasoline and a hundred other things we don't have yet.
But breeding dustmites?
Sigh.
Do you then on releasing them into the wild or selling them door to door?
We already breed dustmites; just by accident. The incubators are homes, the climate controlled by the choice of laundry detergent and thermostat. This wouldn't be much different. A starting point is just measuring the allergen content of the particulates.
In any of these projects the dominant cost is salaries, which are not so high if you hire great young people who care about it. It only seems impossible to those with a lack of imagination.
As for selling them, here a market for you: ecologists with asthma. These probably number in the low ten thousands, they probably spend close to a thousand dollars a year in medication, and four years in lifetime. That's hundreds of millions in that market category alone.
