It might cost pennies for wealthy countries but might be a good chunk of money for poorer countries.
People from wealthy countries usually forget about the rest of the world, when they talk about things that annoy them.
That said, if you're running a hobby site that only targets people from a poor country, the money has to come from them anyway, be it from ads or from donations. In that particular situation, why would ads bring more money than donations compared to sites targeting people from richer countries?
I am from Spain where the minimum salary is around 700$ and has 40% of young people unemployment, however it's not poor compared to most other countries and the hosting cost is considered cheap.
I don't know what could they do where the hosting cost is significative. Do ad networks scale prices depending on the country served?
I think that's the ugly side of global capitalism as the answer is they shouldn't launch sites then.
Maybe they could try to join several groups to share the expenses. Any other ideas (besides advertising)?