This will sound rude, but are you trying to fool others are have you just fooled yourself? Comparing a restricted store which only allow a few marked freemium games, with the PC game market in general is ridicules. The article is about the PC market and PC pirates. Not only is the PC market massive bigger than the total of 588 titles since 2004 that XBLA has, but XBLA has less freemium games per title than the PC market has. They also have a different demographic. A XBLA users is average ages 22, is a causal gamer, and has a middle class income. The average PC pirate age is lower, has less exposable income, and preference more hardcore game.
There is no shareable trait between the PC pirate, and the XBLA market. Trying to present the PC market as if its somehow would be the limited selection of XBLA titles is just false. Presenting a small selection bias as representable for the game industry is just...
[1] says it was 18% in 2007. I very, very strongly doubt it's gone down. XBLA de-lists games with a Metacritic score below 65 (which is basically impossible) and a conversion rate below 6% (which is apparently really hard, huh?)[2]. Ken Lobb has referred to 20%-40% conversion rates for in-house games at MGS.
And you once again are bound and determined to ignore the differences between the markets you want to compare (hint: they're not identical products, they're not even substitutable products!), I think I'm going to bow out because there's no progress to be made here. HAND.
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[1] - http://www.gamasutra.com/php-bin/news_index.php?story=15117
[2] - http://www.joystiq.com/2008/05/22/underperforming-xbla-title...