Indeed, EPEX spot prices are between €0.30 and €0.39 today including taxes where I live. I've seen them go up to €1.10 during peak demand.

it is not the marginal price for household users, but the (average electricity bill : subscription + consumption) / (average consumption), so it will be higher than the additional kwh consumed.

Maybe, but only it's marginally off.

This is what I pay extra per kWh,in Netherlands: € 0,25162 ($0.291), excluding the connection costs.