Maybe I'm misinformed. Which Thorium reactors worked reliably and cheaply?

You're not misinformed. Commercial thorium doesn't exist and prototypes have issues with proliferation risks and the lifecycle of the materials used to build the primary containment. It is promising and there are several groups working on these problems but it's a hard sell given that recent gen uranium reactors aren't gated by fuel costs and have established supply chains.

Indian Point tried thorium. They abandoned it, for reasons.