Not to be mean, but this is a little ignorant. The areas in which Gates does his work are extremely impoverished. Getting food is a real issue, having a bed net is a luxury.
In 2001, 1.1 billion people had consumption levels below $1 a day and 2.7 billion lived on less than $2 a day.
When you're living with such an income, you're probably starving and hoping you make it through another week. Even if it were possible for someone to save the amount needed, there may still not be a shop around where you can buy one, especially in rural areas.
Eh, if people can buy clothing, they can buy a net which is a cheaper item. They cost 15 dollars on amazon, and the wholesale price is probably about 50 cents. It's not like the whole continent is still living with bones through their hair,