I'm gonna agree that they just haven't been cared for properly. I've seen rbps stay the size of a nickel for months and grow to 3-4" (plus get some color finally!) in less than 2 months with proper care.
Around here P's sell because they'll viciously attack a goldfish and that's it. When I took over the fish room at a LFS I switched them onto prepared and frozen foods with live insects/worms. They grow like weeds but they don't sell often because I won't throw a goldfish in there to show how "dangerous" they are.

Even with three 7-10" rbps all anyone wanted to see was them attack fish. When I occasionally gave them convicts it killed sales because people were disappointed that they hunted rather than frenzy and crash into glass to catch them.