That's the reason Pac/Bradley 2 did less numbers than Pac/Bradley 1. At the time of the first fight Pac was the #1 or 2 fighter in the world, while by the time the rematch happen he had fallen from the top after that Marquez KO.

Floyd/Maidana probably didn't do as many numbers as normal because most people didn't give Maidana any type of chance. Floyd gets a big chunk of his buys from people that don't like him and want to see him lose - those types of PPV buyers may have sat out the first fight, but after seeing that it was a closer match than expected (and I'm sure there's plenty of Floyd haters that are saying he should have lost) they'll definitely pay to see a rematch.

That is, unless Floyd fights someone else first and gets knocked out, like Pac did.