I honestly have no idea about healthcare costs in countries like that, but assuming the main cost is a surgeon, the reported median salary for surgeons in Sweden is between 110-150k usd yearly. Assuming 200 working days a year and available for something like 4 surgeries a day on average that goes to about 137 usd per surgery. Adjust for Malawi being a far cheaper country but addition of more staff and a cost of 400$ for a relatively minor surgery doesn't seem too far fetched if there isn't middlemen taking a cut (actually googling it seems like middlemen can take a fairly large cut even with those costs).