Thorium energy is cheaper than energy from coal, in fact there is more energy in the form of thorium in coal ashes than in coal itself.
Coal Combustion: Nuclear Resource or Danger a review by Alex Gabbard says: “Consequently, the energy content of nuclear fuel released in coal combustion is more than that of the coal consumed!”
The Most Important Investment that We Aren't Making to Mitigate the Climate Crisis The Huffington Post
Coal Combustion: Nuclear Resource or Danger ORNL Review
Coal Ash is More Radioactive than Nuclear-waste Scientific America