That's the problem: people see Pac (or any other fighter for that matter) do things against a tailor-made opponent like a Brandon Rios and assume he'll be able to do it against anyone. Those people are going to be gravely disappointed.

Against the big plodder Margarito, Pac threw over 1000 punches. Against Brandon Rios, well over 700.
In the 3rd Marquez fight, he threw just over 500. In the 4th fight, over 6 rounds he threw 256 punches, so he was on pace for about 500 punches. That's about 40 punches a round against Marquez, so the amount of punches Pac throws is totally dependant on the style he's fighting. And keeping in mind that Floyd is a much better technical boxer than JMM, much longer, much better defensively and much less likely to stand and bang... those who think Pac is going to have this huge punch output against Floyd are going to be sorely disappointed.