

It depends and varies wildly based on your area and how the electricity is actually sold.
If they are using an energy stock exchange, as many places are, then increased capacity, especially increased renewable capacity, greatly reduces the price per kWh because the price depends on the most expensive method of generation.
And because renewables always offer their electricity for free to the exchange, as they don’t have any fuel etc costs, you sometimes end up in the peculiar situation like here in Finland (and in the entire NordPool area) tomorrow between 13:00 and 16:00, where electricity is literally priced at 0€/MWh, as there is enough renewables to cover it all.
From what little I’ve researched about privately producing back to the grid here in Finland, it really didn’t make much sense. You get terrible rates and as you said have to pay the transfer fees too. It’s priced in a way that they clearly would rather you didn’t do it at all.
But the NordPool isn’t really a system designed with tiny private producers in mind. Price goes to zero, or sometimes even negative, exactly to try to prevent having to pull electricity production down as that’s expensive and complicated. It’s clear to see that it isn’t a sustainable model in the long run, but hopefully it incentivises companies to build the solution - storage - to make use of all that “wasted” energy and stabilize the price and market.