Please provide evidence to back that claim up.
Reposting this from pg 2 since I know ppl don't read anything but the first and last posts
VGChartz generally underestimates pc sales by 30%-50%. This is based on their numbers vs cases where a publisher actually reveals the breakdown of sales by xbox/ps3/pc instead of reporting them in aggregate. Its also generally reported that pc retail vs pc digital sales are 50/50, with steam making 70-90% of digital.
Ex. VGchartz reports 0.68m for the witcher 2; CD Project released figures of almost 1m sold. (CD Project is the publisher, they know exactly how many copies were on steam, GoG, retail, or anywhere else.) http://www.eurogamer.net/articles/2011-11-10-cd-projekt-witcher-2-gog-com-sales-vindicate-drm-free-decision
So ~2.6 to 3.6 mil for skyrim on pc is a safe bet, depending on whether you believe the retail vs digital sales breakdown for skyrim is similar to the witcher or closer to 50/50.
PC: 2.6 to 3.6 million copies
360: 5.29 million copies
PS3: 3.14 million copies <- Probably would've sold ~4 if skyrim didn't run so poorly on PS3
I'd guess closer to 2.6-3m since RPGs tend to skew towards people who care about physical collectors editions and older gamers who favor retail, and this is the latest in a long line of games in an established RPG franchise. Also don't underestimate the number of digital download conspiracy theorists and people with bad internet.
As opposed if this were say... Assassin's Creed or Borderlands which skews towards younger gamers who favor steam over retail for the social/convenience factor. Then I'd guess the breakdown were closer to 50% retail/50% digital, or even 60-70% digital.