It would be good to have more analysis of this.

Is saving someone from malaria really the most cost-effective way to speed technological progress per dollar?

The answer is that I don't know. Perhaps it's better to fund technology directly. But the benefit:cost ratio tends to be incredibly high for the best developing world interventions. So the best developing world health interventions would at least be contenders. In the discussion above, though, preventing malaria doesn't need to be the most cost-effective way of speeding up technological progress. The point was only that that benefit outweighs the harm done by increasing the amount of farming.