You assert that the cost of fighting disease has increasing marginal costs. It is probably true that the cost of physical acts like distributing mosquito nets has increasing marginal costs. But we should test this and find out how fast it grows. Moreover, the sign of the marginal change to deaths/net is really not obvious and has to be measured. It might go down as you run out of people who would use them. Or it might go up, as you achieve herd immunity; or by keeping transmission out of houses, you might cause malaria to evolve to be less debilitating.
PEPFAR is a counterexample to your claim. Its original implementation had poor effectiveness per dose, in line with predictions. In 2006 it switched to generics, expecting to increase effectiveness per dollar by a factor of 10, leaving it still ineffective per dollar. But increasing doses by 10x turned out to be much more than 10x as effective. It is quite mysterious why its effectiveness improved, the best candidate being herd immunity.
You assert that the cost of fighting disease has increasing marginal costs. It is probably true that the cost of physical acts like distributing mosquito nets has increasing marginal costs. But we should test this and find out how fast it grows. Moreover, the sign of the marginal change to deaths/net is really not obvious and has to be measured. It might go down as you run out of people who would use them. Or it might go up, as you achieve herd immunity; or by keeping transmission out of houses, you might cause malaria to evolve to be less debilitating.
PEPFAR is a counterexample to your claim. Its original implementation had poor effectiveness per dose, in line with predictions. In 2006 it switched to generics, expecting to increase effectiveness per dollar by a factor of 10, leaving it still ineffective per dollar. But increasing doses by 10x turned out to be much more than 10x as effective. It is quite mysterious why its effectiveness improved, the best candidate being herd immunity.