They’re saying that the cost of providing electricity to the cities, where everything is densely located and there are fewer trees and fewer overhead lines needing under grounding is lower so they should charge less to city consumers.
They imply that the bulk of the cost is delivering power to the richer consumers further out because there’s a lot of line miles that need under grounding. That’s probably accurate.
But utilities are restricted from pricing like that because you don’t want utilities triaging customers that are less profitable. The article here makes the argument that the far away and expensive customers are rich, therefore fuck ‘em. I’m not familiar with California but I doubt this is true across the board. There are surely notably rich communities far from the city but surely there are also poorer areas further from the city that are relatively cheaper because the commute is worse.