I think there is a moral dilemma when someone creates something immensely valuable, but wants to be paid for it. But... wouldn't a world in which people didn't get paid quickly become rotten? And is it any different from people needing money for life-saving surgery (because the surgeons, hospitals and suppliers all want to be paid). See also the pied piper.
Factual content: there's a camping device for purifying water with ultraviolet light http://www.steripen.com/ but it just kills things, and won't remove salt or arsenic.
Now if we take grinding poverty as a per capita income of $1/day and consider a village of 100 people, that means everyone in the village could have 5 liters of pure water a day at a cost of 1 day per week - a 14% 'tax' for 1 year.
That's a big economic hit for a very poor village, but it would not surprise me to find that such a village might lose more than 14% of its productivity to a combination of acquiring cleanish water and lost productivity due to water-borne diseases.
$5200 is not big bucks to us in the developed world. Surely it would not cost too much to buy 5 of them and do a year long comparison of 10 villages where half of them have the system and the other half serve as a control. Even if you add in setup costs the total bill for such an experiment would only be $75k.
It costs WAY WAY too much. He "hopes" to get it below $2000, which means right now it's more than that. And after you read the $/L estimate, add in the cost of fuel and you'll see the device is not cost effective (when compared to other devices that do the same thing).
According to here: http://www.ecofriend.org/entry/powered-by-cow-dung-slingshot... the system cost is $5200.