IIRC the real costs of residential electricity are about half from infrastructure, half from actual energy consumption [1]. If we charged prices proportional to costs, high users would still pay significantly more than average users. The main problem (a political one) is that in a lot of places these costs have been bundled together in a single "per unit" charge that effectively subsidized the lowest consumers. Changing it so that prices go up at the low end of consumption and go down at the high end of consumption would widely be seen as unfair, so it's hard to correct the pricing mistake now that it's ossified into place by tradition.

[1] It's different for big industrial users, like factories operating 24/7; their per-unit costs are dominated by consumption rather than infrastructure. They also get lower prices partially reflecting these lower costs.