Surface RT, a 10.6-in. tablet, went on sale starting at $499 on Oct. 26.
The 10.6-in. Surface Pro, formally called Surface with Windows 8 Pro, will go on sale in January, starting at $899.
Analysts say sales of the Google Nexus 7, which launched in June for $199, is now at about 1 million a month, up from 500,000 early on. Apple, meanwhile, has typically sold several million units of any of its iPad tablets and iPhones in the first few days of sales.
Microsoft today didn't respond to a request for comment on its sales or retail strategy.
Matt Hamblen covers mobile and wireless, smartphones and other handhelds, and wireless networking for Computerworld. Follow Matt on Twitter at @matthamblen, or subscribe to Matt's RSS feed . His e-mail address is email@example.com.
Read more about tablets in Computerworld's Tablets Topic Center.