Each panel is a financial cartogram that compares things within the panel to each other by showing the amount of money as an area. That's exactly what the top comment was doing -- making an analogy to a physical unit to make the comparison more visceral and intuitive.
You may notice that comparing things across panels is more difficult than the effortless comparison of two categories within a single panel. It's easy to understand conceptually when you study this map that the insurance industry in the US is a lot more money than Kate Middleton's wedding dress. But you don't see visually and immediately how much more money, because they're not side-by-side in the same units.
On a log scale, plotting everyone's income puts Bezos and Gates side by side with very little visible difference, while the difference between someone who makes 20k a year and someone who makes 10k a year has a larger log difference. That emphasizes the ratio of difference, rather than the absolute difference. The log scale completely hides the fact that you could pay 75,000 people 20k a year with only the amount extra that Bezos has over Gates.
You can also give decent salaries to a lot of African people with the 10k difference between the 20K/year person and the 10K/year person... so what's your point :) ?
So you just answered your own question. The absolute difference is worth a lot more. It's better to have the $1.5B difference between Bezos and Gates pay Africans than it is to use the $10k between our two people in poverty, even though one makes more than the other.
Your suggestion to use log scales hides that fact, and shows the ratio of $20k to $10k as visually larger than the ratio between $92.3B and $90.8B. That is why log scales are counter intuitive and not great for physical analogies. You asked, I answered.
We couldn't even put all people on the same linear scale if we wanted to ^^ . It would look like : almost everyone at the bottom, and some people at the top. So yeah, it would be obvious then that the only money we could take is located at the top points.
Nitpicking but... Africa is a big continent, with a great deal of nations, and a large variety of income levels, with some of those incomes much higher than yours.
You may notice that comparing things across panels is more difficult than the effortless comparison of two categories within a single panel. It's easy to understand conceptually when you study this map that the insurance industry in the US is a lot more money than Kate Middleton's wedding dress. But you don't see visually and immediately how much more money, because they're not side-by-side in the same units.
On a log scale, plotting everyone's income puts Bezos and Gates side by side with very little visible difference, while the difference between someone who makes 20k a year and someone who makes 10k a year has a larger log difference. That emphasizes the ratio of difference, rather than the absolute difference. The log scale completely hides the fact that you could pay 75,000 people 20k a year with only the amount extra that Bezos has over Gates.