There are over 18 million active WordPress blogs at the moment. It's a huge market. I spent a couple hours building a WordPress plugin and sold $200,000 in licenses for it in a year and a half.
I've made about $8,000 in sales selling my own theme modeled after the site I built for iJustine (theme link: http://whalesalad.com/tasty) but that's just a teeny fraction of what you made, let alone Woo! I have more in the pipe... but there's only one of me =/
I'm assuming this isn't sensitive since it is listed in his portfolio: it helps affiliate marketers build review sites on top of Wordpress, and costs about $100 a license.
