In my experience I have never seen a used PX4 .45 that was used much. Either they did not like the heft or recoil or something...and sold it... Or they like it and keep it.
I deal with a large number of PX4 owners and quite a few that have PX4s in .45 ACP. Those that have a .45 love it, but don't shoot it a lot.
So, "used" is a relative term.