Well, the moral and true answer is that invest into the developing world until everyone has the ability to earn a living wage and can afford small fees like this should they choose.
This is just a general point about globalisation and selling to different markets. Obviously, a YouTube subscription should cost a Liberian a proportional amount, not the same as a wealthy US citizen. Do YouTube advertisers make as much money from the average Liberian as they do from the average American?
YouTube is a US company with US costs. It might not be worth it to provide the service at a rate that Liberians can afford. The reason they do so now is because the ad-driven model allows them to extract a lot more value out of the US (or other more affluent) customers than those people would reasonably be willing to pay for.
One wonders if there's be a lot more local competitors to services like YouTube in an ad-free world, then. Where the revenues would boost the local economy rather than US.
