There's one market for grid delivered electricity because within the grid, electricity is mostly fungible. There's details of course, but if I need X kW @ 240VAC to run my house, business, or factory, my equipment doesn't care if it's from wind, solar, nuclear, or lemon batteries, as long as it's within the specifications, well synchronized and continuous.

There's some amount of market preference for different generation types, but that's a small portion of the load, so it's handled outside of the grid operation marketplace. It's also true that grids with limited interconnection have separate markets.

You could run a grid on a cost plus basis, but you lose the benefits of market economics as well as the negatives.