Sure, it's a marginal price. It is surprising to me that HN struggles to understand marginal pricing, it makes me more likely to assume when I see such people unhappy with taxation that they probably also don't understand marginal taxation.

Marginal differences have a cliff effect, which is one of the things US Republicans are worried about in the event Trump isn't able to subvert or abolish entirely this year's elections. If you've gerrymandered every seat so that you'll win by 3-5% and then your support collapses 10% across the board then you lose all those seats, not 10% of them. Ouch.

For that 1% in reality it's probably not quite the case, my understanding is that most of the gas plants pay a significant price in terms of efficiency loss and wear on the turbine, for restarts, so e.g. make 10MW for an hour, switch off for an hour, then make 10MW for an hour is 20MWh produced, but incurred a stop-start. The 20MWh might equate to £1000 of gas burned, but the stop-start has an effective price of £500. So you need to charge £75 per MWh to break even. Or, you could sell for £60 per MWh, deliver 10MWh for all three hours, 30MWh, £1500 of gas burned, no stop-start overhead, your overall costs were the same but you got more profit because 30 x £60 = £1800 instead of 20 x £75 = £1500.