It was a really hard business model to support and get to work. You are paying for the forward belief that the network itself will be strong enough to ultimately justify the costs, but over time if that belief isn't met (and it wasn't) then you will lose subscribers.
I give Dalton and Brian kudos for trying. Ultimately I think the lesson here is users simply aren't offended enough by ads that they would be willing to pay a subscription service to avoid them.
I'm not even sure the dollar price was the issue. But I would have to rebuild things like "people to follow", get used to the new interface, have the risk that the platform doesn't survive - a lot of implicit costs. What could be working is to offer a paid tier for an already existing service like Twitter - but unfortunately they have a strong incentive not to. Because it would mean that their ads would stop reaching the very people that the advertisers are interested in - the ones who are willing to spend money.
I give Dalton and Brian kudos for trying. Ultimately I think the lesson here is users simply aren't offended enough by ads that they would be willing to pay a subscription service to avoid them.