You need to choose a very carefully targeted charity that takes into account knock-on effects like displacing local production, before you should accept any such claim. It is now being suggested that the majority of aid is actually counterproductive and destroys local industry in exchange for giving Westerners a warm fuzzy feeling. Hence Africa staying poor despite (because of?) hundreds of billions spent.

Frankly, if you're going to put in that much work into buying expected utilons at the cheapest available price, you shouldn't be considering any mainstream charity targets like aid to developing countries. Let Bill Gates worry about it, if that's the limit of his creativity.