Coal is not the cheapest: natural gas is. Onshore wind actually costs about the same as coal, and less than nuclear. Offshore wind is currently about 2.5 times more expensive.
Solar photovoltaic (PV) currently costs a bit more than twice as much as coal, and already less than offshore wind.
The table does not take into account the environmental costs of the various power sources, or obviously coal would fare far worse, and biomass would not be rated anywhere near as good as wind.
Remember, the cost of solar is falling rapidly, so solar will rapidly become more cost-effective compared to other energy sources.