> All those gas plants and batteries sitting around idle soon start dominating the cost structure because the price of their produced watts starts to go exponential.

When they're barely used, price per watt stops mattering. It's just a fixed cost.

If the fixed cost of an idle gas plant dominates, that's a good thing. An idle gas plant doesn't cost that much, so if the final power price is that plus 50% I'm pretty happy.

If batteries are expensive for long rare gaps then don't use batteries for those gaps. Easy.