I don't think this is true. I live in Canada and the worst costs involved in charging my Tesla at a supercharger are maybe $20 for a full 'tank' but compared with $100+ for a gas car given gas prices here there's no way this is true. Here in BC there's a ton of charging competition too, so you can find far cheaper than superchargers—plenty of places where I live offer free fast charging right now if you look for them.

Also, most of the time you're charging at home. In BC, electricity prices are $0.09/kWh... so dirt cheap.