This NYTimes post talks about designers like this:
The world’s cleverest designers, said Dr. Polak, a former psychiatrist who now runs an organization helping poor farmers become entrepreneurs, cater to the globe’s richest 10 percent, creating items like wine labels, couture and Maseratis.
How true is it!! Even I belong to the 10% domain. What if designers divert their attention towards the poorest of poor and design things for them that is very economical? The world might probably see no poverty after some generations.
The article also contains some snippets of those designs that are currently in the marker and being used by poor people. I think the product of two factors – number of customers and revenue per customer is what matters. I mean, by concentrating on the 90%, the first multiplicand increases and the second one decreases with the net result mostly same. May be it is not as straightforward, but it sounds feasible enough to make business out of it.