Including whomever wrote the article.
"Suppose, a litre of cola costs US$3.15. If you buy one third of a litre of cola, how much would you pay?"
As cola has a large size-indpedenent cost, I would reasonably expect to need to pay more than the claimed $1.05 if 1 L is $3.15. Moreover, the marginal utility of 1 L isn't 3x more than the smaller container. There is no need to have that much soda when an appropriately scaled option is available. Based on real-world prices I could find (YMMV), 1 L of cola sells for $1.99, while a can (355 mL; about as close to 1/3 of 1 L as we find for actual sale) sells for $1.69, echoing that $1.05 is not a realistic price to pay on the open market. Most importantly, in actual practice I'd pay nothing for cola and order water instead.
And he is supposedly a lecturer in Economics and Social Statistics at a fairly well respected school. Goes to show, again, that the kids won't learn unless they want to. Forcing teaching upon someone plain doesn't work. Never has, never will. Incentivizing one to want to learn can work, but that's something else entirely and not at all what we're talking about.
Most kids would never go to school if not forced. They'd play video games or watch youtube.
There are 0.7 billion adults that can't read. 40% of adults in 1st world countries can't do arithmetic.
https://theconversation.com/high-number-of-adults-unable-to-...
So, no, there is no evidence people will not learn without being made to learn. There are only anecdotes that some children get lucky and learn things on their own. That's not the norm and there is ample data to back that up.