The fines for rigging Libor were big. But get ready. Fines for rigging the foreign exchange markets could be a lot bigger.

The Libor-rigging litigation has already netted $3.5 billion in "settlements" with regulators, with several others expected soon. It's already clear that the fines aren't related to the size of the profits made from the misconduct, which is neither admitted nor denied. Instead, the amount of the penalties appears to be tied to the enormous size of the markets that use Libor in setting rates.