The reality is rather different. We need to say more about the three main products traded, and introduce the notion of relative values. We may then find a very different result, a rather Panglossian one where it seems everyone did well, a confirmation of Abu-Lughod in fact. This is primarily because of the notion of relative values. A society can export products which it does not value, but which are valued in other areas.
Goods then have a cultural as well as a material value.
This would seem to account for the massive profits which the traders, nearly all foreigners, made. In the case of gold, it was little use in a non-monetised society, but in one like India which in the early modern period was monetising rapidly it had an obvious demand. So also with slaves, essential for west Indian and Brazilian plantations, but not in great demand in Africa except for some domestic and minor agricultural work. And so also for beads, produced in massive quantities in India for little cost, but highly prized in Africa. The concept of relative values applies most clearly to the trade in ivory.