It's boring to frame Mastodon as a Twitter usurper and much more interesting to think of it as an experiment for techno-socialism.
While users don't "buy" Twitter, Twitter sells user data to companies looking to make a profit off of users. People who have the means to create or support Mastodon instances provide the "service" for free. $ and tech skills get re-distributed to a wider community. Nothing and nobody is bought and sold.

@amy I think this model also makes a difference as far as incentive to get rid of troublemakers. If your business model relies on attracting advertisers by telling them you have X million users, you might not want to do anything that will lower that number.

A distributed service based on people contributing time/tech out of principle receives no benefit from trolls—unless trolling is the point—and is more likely to recognize that trolling hurts the community.