Most people think that, all other things equal, higher prices lead to lower demand. This is obviously wrong for goods which are bought because they cost a lot of money, like wine. But it can also be wrong for another kind of good.
Imagine you find yourself reborn very poor. With 6, when you first start to actually 'think', you find yourself alone, completely uneducated and with no possessions at all. Your picture of the world is massively lacking but you do understand your immediate surroundings. Somehow you manage to make a living.
Most of the time you buy the cheap but nutritious product A to survive. For example potatoes, or rice. Usually you also have a little bit of money left. This money you spend to buy the occasional product B. For example a fruit. It's not as nutritious per dollar but tastes better. Now imagine that the price of product A increases. What happens?
Let's assume that on average your body requires a few hundred calories per day, which is a pretty conservative assumption. But we are not talking about western-style living here. Before the price increase, on an average month, you satisfied this requirement by eating a lot of product A and a bit of product B.
But now, after the price of the cheap, but nutritious product A increased, you cannot buy the same amount of product A and product B anymore. What do you do? Well, you could continue to buy the same amount of product B every month, and just less of product A. But in that case you would starve to death. Consequently, you will continue to buy at least as much of product A as before. Which means that you cannot buy as much of product B.
But you would still starve to death. You require a specific amount of average calories per day and just scaling back on product B enough to consume the same of amount of product A as before would leave you short on calories. Your stomach strictly disagrees.
Product B might be tastier, but it is not as nutritious as product A per dollar. That's why you continue to scale back on product B to buy even more of product A than before the price increase. And thus a higher price has lead to more demand.
You might still die early because product B was necessary for your health in the medium-term. But at least you satisfied your calories-per-day requirement and didn't starve to death.
Such circumstances are difficult to find in reality - especially in this pure form. But the example shows that classic economic theory does rely on assumptions that aren't always correct. In the given situation the idea of 'competition' in 'free markets' for the 'greater good' is turned upside down; even (especially) if all actors are perfectly rational.