Earlier quoted context omitted.
That is how literally everything in a market gets priced. When you buy an X, the price of it naturally trends to match the most expensive X that will be sold. In this case X is a watt of energy. But you can substitute any good or service.
Can you explain this? In commodities market, the strike price is between the lowest price seller and the highest buyer. In the goods market, individual buyers buy depending on their elasticity of demand unless the good has inelastic demand (rare). Neither matches what you seem to say.
The lowest seller price is the highest demanded price among all the sellers. All the sellers bar one would typically be willing to sell for a slightly lower price. As it is said; prices are set on the margins.
Imagine that every seller has a secret price they are willing to sell for and that is some statistical distribution. The market price will be the highest price in that distribution that actually gets sold. Most sellers aren't selling for their secretly acceptable price, but for a higher price determined by the seller with the highest demands. The distribution, if it is ever discovered, becomes the supply curve.