Looking at the global median income and coloring it with the mean revenue per user paints an incorrect picture. Advertisers are not paying even $35/yr for the attention of people making the global median wage.
US attention is the most valuable because it is the richest large nation and the largest rich nation.
European attention comes a distant second. Together they have 40% of the global GDP, but likely something like 60-70% of the consumption of non-essential goods in nominal terms. Accordingly, average advertiser cost per clock differs ~10x between the cheapest and most expensive groups of countries.
US attention is the most valuable because it is the richest large nation and the largest rich nation.
European attention comes a distant second. Together they have 40% of the global GDP, but likely something like 60-70% of the consumption of non-essential goods in nominal terms. Accordingly, average advertiser cost per clock differs ~10x between the cheapest and most expensive groups of countries.