Don't get me wrong, I know the cost is near zero for the actual products. It's the logistics that's expensive. The fact you can get a bag of plastic bits collected from all over Shenzhen to your house in SA within a couple weeks and for a few hundred bucks is nothing short of remarkable.
A single lens from New York cost me R 1000 to ship, plus customs clearance fees on top. A few sheets of paper cost R 600 to get to the UK.
With Temu you pay something like a Rand per gram for air freight, and the actual product is essentially free. It's nuts. So I doubt it's profitable when fully/reasonably accounted for. China has massively distorting subsidies all across their economy, for one thing.