If you give me a 50% cut I'll buy it :
Eh? It's only $9.99 and you get an extra free game too you cheapskate! ;-)
As for sales figures, I'm curious too! But I may not be able to be specific about Steam - think they have an NDA in effect. I've been searching for Steam sales figures on the web and the only info I've found is that Audiosurf made its author a millionaire in a few weeks (I can hope but really don't think TU's going to do that!) and that Darwinia sold 17,000 copies in about 5 months, two years ago.