I do not think that the price is the attractive thing in using a VPN because there are many services that claim to be free, but some other factors may make the user pay up to $ 20 a month, the most important of which are:
Speed, the cleanliness of the IP address, and that it is not prohibited or known to the service providers with the ability to hide the main address using Tor or any other service.
Not to mention that almost all VPNs offer the same thing and the things that they advertised doesn't necessarily means that it is true, there was a video by Tom Scott about VPN and in that video he debunks the things that most VPNs advertise that they do. The only one that really works well is Tor browsers combined with Arch Linux.