> Oh, I don't remember the website mentioning this. How does this work, and what are the implications?

You can read about it here (bottom): https://1sub.dev/about/how-it-works

It means that there is a supply/demand that influences what price the subscriptions can be sold for. Developers have a limited number of "credits" that can be turned into subscriptions. They can get more credits by making people subscribe through their links. There is also a plan that the credits will be multiplied and grow with time in order to keep the prices on a sane level.