One aspect is perhaps that simple things aren't necessarily cheap. One Laptop per Child struggled to get costs down, whereas a mass market solar panel is not self-serviceable but at their current cost, who cares. Even in the developed world, you get noticeably more bang for your buck if you buy a cheap, basic car than if you buy a cargo bike that could replace it, because of the fierce competition and huge economies of scale for cars. Touch screens are cheaper than seven segment displays. And so on. (Not a snub on the Open Source Low Tech community, their designs look great!)