It's more of a thought exercise because he was making a point that people would expect all users would disappear if there was suddenly a fee like that (for everyone), which, invariably would affect how much the product is worth to them. That's why this only works backwards - asking people to quit for a reward.
If everybody has to pay $1000 a part of your network will disappear due to not having the sum available regardless of the value of the service.
Then everybody else would have to decide if the rest of the network still provides value to them, so a few more would disappear. At some point you'd reach an equilibrium where either a small portion of the original network is happy with what they still have for the money, or the whole network collapses.
It doesn't feel like people would quit because of the expectation that "everybody with any sense would stop using it". You could already say that now about FB, and you could definitely say it for many other products. Yet they are still used.
