My friend and I just bought the Mephaquin antimalarial medication in Nairobi, Kenya. Since we’ll be in Kenya for another 3 weeks, and then Ghana for a month volunteering with Lumana Credit, we bought 8 weeks worth for 1500 Kenyan Shillings (about $19 US dollars at the current exchange rate).
The malarone antimalarial medication, which I believe is the most effective, was about 3 times as expensive at about 2000 Kenyan Shillings per 4 week dose (so 4000 Shillings for 8 weeks).