> The equipment that sits around waiting for low or negative electricity prices represents locked up capital, and ongoing maintenance and depreciation costs

But the costs over time are negligible when current alternatives will eventually only go up due to scarcity. I might be missing something.

> But the costs over time are negligible [...]

In heavy industry, they're very much not. Large machines often cost large amounts of money. You don't want large machines sitting around doing nothing when they could do useful work and earn money instead – so that you can, for example, pay off the loans you took out for them, or pay the operational staff that pulls the levers and turns the switches.