Specifically burying the lines so they survive forest fires.
I agree that it doesn't necessarily reflect the individual marginal cost of an additional customer, but that makes sense, things rarely do.
Most things in US are super costly because of monopolies, regulatory capture and perverse incentives: https://en.wikipedia.org/wiki/Perverse_incentive
They're doing well globally, and solar is generally ramping up quickly everywhere but headlines are more often about hitting 100% renewables for an hour or for a day, not over a year.
Which would be home solar and storage
Also, my pge statements now have a line item for transmission that's usually larger than my generation total. If I have 2x solar and I'm feeding my neighbor, are they paying the same "transmission" structure for the power I'm providing them?
Repowering a solar or wind power plants is dramatically cheaper than building it from scratch.