The majority of the cost of electricity in most jurisdictions is distribution, not generation. Grid-solar still requires distribution, so it is always going to have significant cost even if the cost of generation is insignificant.
If it can remove the need for a grid-tie, then rooftop solar can be significantly cheaper and more efficient. Can be, but isn't yet, because enough overcapacity and storage to eliminate the need for a grid tie is still too expensive.
This is exactly the challenge. Here in California wholesale solar plant sell power for 0.03-0.04 kwh. Cost at the meter is 0.45/kwh.
Rooftop is competitive with the meter price, but unless you can cut the cord entirely, connection fees and rates will just keep increasing proportionally
If it can remove the need for a grid-tie, then rooftop solar can be significantly cheaper and more efficient. Can be, but isn't yet, because enough overcapacity and storage to eliminate the need for a grid tie is still too expensive.