I think the point is that actually doubling income is a better way to increase income than trying to optimize the price of one product.

What we do know is that food is already very cheap in Africa. It's not obvious that food could get much cheaper, let alone the 300% price reduction that you give in your example.

On the other hand, we do know there are huge gains to be had when it comes to increasing income and economic activity in general. That's where our effort would be best spent.

This is literally creating local jobs. A job equals more income than no job. So this is raising incomes. In addition, there's less capital leaving the country buying foreign produce. So the money that would be spent anyway creates a local job, and in return is again spent locally by a Ghanaian farmer, instead of spent in Europe by a Dutch farmer. This is literally a win all around. An economy is a system, you can't just one day create amazing jobs without an entire support system around them.

If they're importing a large amount of their food from Europe as the article states they very well can lower the cost by producing it locally. Even if they're less efficient than the Europeans in doing so.

I'm not sure they can, actually. The wheat fields of Kansas or the Ukraine are so vastly more productive than trying to grow crops in a tropical climate.

Plus a lot of those fields of grain are subsidized during times of plenty for national security (and other) reasons.

If food prices drop, won’t farmers make less too and hence lower income?

Maybe I am not understanding the math properly. Food is cheap in the USA because we import them from poorer countries where labour is cheap. And we also consume a lot. This benefits the exporting country. But if we were to produce our own food, the local production won’t be cheaper.

You can do that in two ways: Reduce cost of food by two thirds or double their income.

Both of these feats would be incredible. So yeah, if we could do incredible things, that would be amazing.

Let's get back to reality though: Food prices are more or less set by international markets. African farmers can't compete with other countries, because they work so inefficiently. Making more people work as farmers doesn't change that.

That's the reason why Africans import so much food. It's actually cheaper. You don't need more people working as farmers, you would need automation to be competitive, but then less people are actually employed. Even then, this wouldn't lower food prices below market price, because those farmers can now export instead of serving the domestic market.

How do you propose to double their income?