This reminds me the recent HN news item saying "Non profits kill the innovation". But this article makes me think that things are even worse than that. Wordpress should do something to change this I guess.
Besides, they most likely have motivations other than money- there's no way anyone starts making wordpress plugins thinking they're going to get rich (at least I hope not!)
The only thing this price means is that it is difficult to make money by giving away stuff for free.