The power companies themselves do not refine fuel. They don't design reactors. Everything in a nuclear power plant is bought and installed. All they do is run the equipment.
You've got to convince Westinghouse (fuel and reactors), Areva (fuel), and several other secondary companies (need equipment to deal with superheated steam, instead of merely saturated).
If you gave the actual power companies a cost effective and vetted thorium plant design, they would take it. But until then, everyone's eyes are set on Westinghouse's AP-1000 design for the next decade or two.
The fact that thorium takes less processing should encourage fuel makers because it's less work for them, while still selling fuel at a profit. But like a poster said, the actual fuel cost isn't why a nuke plant is hard to build. It takes 15-20 billion to build a 2-reactor plant right now. Getting that kind of funding is what's keeping them from being built.