Protein Insider. Clarification needed.

In issue 207, entitled the Protein Insider, the interviewee states,“As a matter of fact, the top seller in the whey protein market is probably one of the cheaper proteins to make. It doesn’t mean it’s terrible quality and that it won’t “work,” it’s just that they’re playing games.”

If the low quality protein still “works”, then what’s the problem?

I’m sure I missed something, and I’d appreciate it of someone could clarify this point for me.

Thanks