Sorry, my example was not clear enough. Only a small fraction of people use VPN, so the monopoly price in a world with net neutrality basically ignores those p

Sorry, my example was not clear enough. Only a small fraction of people use VPN, so the monopoly price in a world with net neutrality basically ignores those people and charges the optimal price for everyone who does not use VPN. However, in a world without net neutrality, the company is able to charge a different price to those who want VPNs and those who don't (this is price discrimination). So it keeps charging the old price to everyone else, but adds on a surcharge only to those users who want a VPN. In this simple example, it makes an extra dollar per month per VPN-user.