That the market price of renewable power can and sometimes does go to zero is simply a consequence of that the marginal cost of producing additional energy is z

That the market price of renewable power can and sometimes does go to zero is simply a consequence of that the marginal cost of producing additional energy is zero. The market price does not include the upfront cost but depends only on that marginal cost. About the same is valid for nuclear power. Only the upfront cost is higher, and there is a much larger cost for decommissioning a plant. That's the reason why renewable power needs to be subsidized, at least to some degree, and why nuclear power was always subsidized.