There is no reason other than political will stopping the WHO and developed nations from subsidizing the purchase of vaccines for places like Africa. In fact, I don't think there is any vaccine that a country like Sudan could afford to administer without such subsidies. Additionally, I suspect the cost of distributing and administering the SARS-CoV-2 vaccine in those areas is going to dwarf the raw cost of the doses anyway, considering the temperature sensitivities of the front runner candidates.

That said, the person I was replying to was claiming the price was too high for some developed nations.