We get it for around 0.0046 US$.

This can of course be supplemented by the enormous Wind and Solar capabilities in Africa,but the problem is infrastructure and the cost of development.

Even in a fantasy world of free energy there would still be many costs running a btc mine. Electrical switchgear, copper, aluminum, enclosures, the building, cooling, internet+backup, mining machines, maintenance, permits, inspections, security, technical knowledge, etc, etc.. It would never be close to a zero sum game. Margins are thin enough at this point that you can blow away your chance at ROI even with free electricity just on infrastructure costs. Build like the government and procure with no questions asked and be damned, or be the junkyard guy that recycles usable equipment for almost free.

In cases where they actually may be 'free' power, I would argue that it is not so free because:
1. There is almost always a severe limit of capacity of power that is delivered freely.
2. Many of these places are in politically unstable areas, very risky to place any significant assets
3. Power quality tends to be very low, unstable, or power is not available 24/7/365,
4. Poor internet connection, specifically unstable or only high-latency connections available.
5. Someone is still paying for it, subsidized or not, so it may be free to you but someone or some group is still paying.