It's the regulatory framework that makes the economics of nuclear plants so undesirable. You gotta jump through a lot more hoops to build a nuclear plant than a coal or natural gas place. As a result, at this point uranium plants are still not cheaper than coal. These thorium plants would probably cost a lot more than uranium plants -- the advantage is that it destroys weapons-grade plutonium and produces waste that is very difficult to turn into a nuclear weapon. Since it's proliferation concerns and not economics driving the fuel in this plant, I suspect it's heavily subsidized by the Indian government.
Counting the whole cycle, nuclear plants are competitive with coal plants and a whole lot cleaner.