in Walmart flip-flop shoes cost significantly less than much more comfortable slipper shoes made of similar plastic (well, I think even-sven mentioned that the actual cost of a flip-flop is trivially small, in the tens of cents). Further, the wikipedia article http://en.wikipedia.org/wiki/Flip-flops elaborates that the cheap flip-flops are popular among poor people in 3rd world countries.
Well, so why exactly are flip-flops so much cheaper than the slippers? On the face of it, they both have a sole and some plastic thongs glued on top, except the slipper way of having the thongs in an arched pattern is IMHO a lot more comfortable and not likely to traumatize the toes unlike the flip-flop case.
So why can’t anybody find a cheap way of making slippers and get all those poor people switch to them instead of the flip-flops? Or are there some great benefits to the flip-flop design that I fail to see while enjoying my slippers?