Ah, but that's where the best hacks can occur usually where legal or socio-political issues keep the best solution from occuring. Unlike a real marketplace, a co-op is an agreed marketplace, so it won't allow new entrants unless they join. To fix the undeveloped country problem, you just limit to the US first. The perspective should be that individuals who want to contribute their organs to the co-op can, but are also allowed to partake in it later as well.