Africa is probably the most expensive continent to be a tourist. Hotels are for the most part more expensive than in the West (the only places I have ever had to pay $500+ for a regular business hotel room are in Africa) and basic amenities that one takes for granted in the West (eg. safe drinking water) come at significant cost.

$50/day is doable, but not as a "tourist". As someone who goes and lives in a rural village perhaps, but your insurance premiums alone for doing something like that will probably be around the $50/day level.

I concur with the other poster who says that $200-300/day is the minimum that one should budget to safely do Africa as a Western tourist on the cheap.