“But to think that a $25 device could improve someone’s life so much is hard to believe.”
Exchange rate- our $25 might well make him middle class in his own currency.
With the device he went from catching 8-10 rats a day to 20+ a day. With the extra rats (and grain), his wife would cook them up and sell them for 25 cents.
I suppose an entrepreneur with a composting toilet (not sure you would need too much??) could go around collecting crap from folks, dry it/ treat it/ whatever, and then sell it back as fuel or fertilizer.