Unfortunately, Radiohead has remained very tight lipped about the results of their ongoing experiment -- so there's not a lot of good information out there.
The following article from gigwise.com came out soon after the album's release, announcing that the album had sold for an average of $8 per download, and that 1.2 million copies had been downloaded from the site.
http://www.gigwise.com/news/37720/radiohead-net-48million-pounds-from-in-rainbows
Then, earlier this week, web traffic tracking behemoth comscore printed this press release with far more detailed statistics. According to comscore:
38 percent of global downloaders of the album willingly paid to do so, with the remaining 62 percent choosing to pay nothing.
moreover, comScore reports, the average price paid by the willing money-payers was only $4 -- not the $8 average suggested by gigwise's earlier reports.
Today, Radiohead responded to comScore's assertions: http://www.mathewingram.com/work/2007/11/08/radiohead-comscore-totally-inaccurate/
In response to purely speculative figures announced in the press regarding the number of downloads and the price paid for the album, the group’s representatives would like to remind people that… it is impossible for outside organisations to have accurate figures on sales.
However, they can confirm that the figures quoted by the company comScore Inc are wholly inaccurate and in no way reflect definitive market intelligence or, indeed, the true success of the project.”
Apparently, comScore's sample consisted of only 100 people. Oops. So maybe the band did make more that comScore suggests. But how much more? Until Radiohead truly breaks their silence, the world may never know.