Humans pay more though. Nobody will be interested in collecting 1c from hundred million of unloyal readers, prone to changing information providers because then they aren't chained with a yearly sub which can be only cancelled via an international 2-3 hour call to the USA for the price of a whole sub. Journal would sooner get that money from the loyal 100000 readers who will pay 1$ per article. But wait, why do that when they can change 10-20$ per article from 10000 and throw some meaningless loyalty program to them?
Even better, do the american healthcare trick - set a price at say 1000$ per article but allow only big corpos to have some opaque bulk discounts for their employees. Thus maximizing money extraction from richest customers.
Also, ads aren't paying everyone's bills -- hence the paywalls -- so that number must be too low.
(Not to mention the other issue with this: in general it's not ads or micropayments/paywalls -- it's ads and micropayments/paywalls. Hell, if micropayments were feasible, it would probably be all three.)
On the VERY high end the CPM (cost per 1000 impressions) is what, $2? That's 0.2 cents per view. I'll gladly pay 5 cents to read the article, even up to $1 if it's a really good investigative/well-researched piece.