Mesh are connected to internet via NAT. [MESH] -> [VPN/Gateway] -> NAT -> [Internet]
Yeah, but the thing about NAT is that it replaces IP addresses in the mesh, each of the nodes, with a single outward-facing IP address. I can say this since you showed a gateway or VPN connecting the mesh to the NAT. So from the IP protocol point of view, the mesh appears no different than a typical internal network with private IP addresses.
Well it's free of charge. You don't have to pay a fee to the operator. That's a major difference which people are also interested in.