I think the costs are more significant than that. A lot of talented people spent a lot of time thinking hard, finding solutions, crafting answers, testing code, and posting their responses, when there wasn't actually any need for them to do so. The plagiarized posts often seem like good topics, and on some level it's sort of nice to have a local archive of answers. But since those questions were already answered at least once before elsewhere on the web, duplicating that effort is of limited value. (Especially since searching PerlMonks is more difficult than it ought to be.)
That's a lot of hours frittered away, and for what? A couple fools got inflated PerlMonks XP? It's a real boggle that these two would so cavalierly waste our precious time and expertise for something so trivial.