[Ekaros]

Purchasers want to make margin on anything. So they charge this on the seller and then on buyer. Also with how markets work it is not like there isn't risks or need to at least some level forecast how much you will be buying and then selling. So their cut also covers this work.

And finally electricity is a spot market. So there is agreed price for certain period and in some cases market can be distorted and that price can be negative. It could be idiotic subsidies or production that can't be ramped as effectively. Or someone does massive mistakes with their bids, think of trading bots going wrong.