They dont even mention the sales from gamersgate, which would enlarge even more the sales numbers.
This is a clear sign that not only indies do better on the pc, indies are slowly taking over pc. Some crucial points can be infered from this:
1. Though it is XBLIG we're talking about, a place that's the equivalent of sales hell on the xbox, they do mention that on steam alone in less than a week they sold more than in 1.5 years on XBLIG, that's a substantial difference between both platforms. This tells me, difficulty of finding xblig apart, the pc seems to be the natural platform for indies.
2. Regardless of the specific sales numbers and taking into account these games won't appeal to everyone, the type of sales numbers that prompted such a post from the devs means it has to have sold decent numbers on steam. This is rather amazing considering the limited appeal of the game and paints an interesting picture, one where pc gamers are moving away from the mentality of "it's indie therefore it must be shit" to "it's indie, it might be a fun game." This change in mentality is encouraging to watch.
3. Each good indie release seems to sell a lot lately. Going into steam's daily charts and it's not uncommon to see more and more indie titles on the top10. It appears that all digital charts and the words from the indie devs themselves shows indie titles, the good ones, are getting more succesful each release. With pc gamers seeing indies as a good source of fun combined with the low prices, good indie games giving all the features we expect from a pc game and the publishers insistence on treating pc gamers as second class citizens while charging ridiculous prices and the slow but sure migration of pc gamers into indies becomes not only inevitable but actually a change in the landscape of pc gaming, where gamers no longer tolerate the bullshit publishers often spew.