It's almost impossible to predict how much demand there will be in that scenario because the world would be a very different place if that system was the default. And with things that are relatively cheap to make, such as professionally produced YouTube videos, people may only need to chip in a few cents to provide an equivalent return to ad revenue.

Given that people are already accustomed to paying for the promise of future things existing in the form of crowdfunding, Patreon or most subscription services in general, I don't think it would as drastic of a difference as you imagine, as long as the infrastructure is there to facilitate effortless 'investing' into many small things.