After an accidental Web site leak earlier today, Microsoft has officially announced pricing for its forthcoming Surface tablet running the Windows RT operating system. It’ll be priced starting at $499, with “a special limited-quantity pre-order” available at 12 PM Eastern, 9 AM Pacific time on Tuesday.

The Surface with Windows RT will be available in three models to start: a 32GB version for $499, a 32GB version bundled with a black “Touch Cover” (which incorporates a keyboard) for $599, and a 64GB version also bundled with a Touch cover for $699. Software pre-installed on the tablet includes a preview build of Office 2013 Home & Student Edition, which will be updated to the final version for free once it’s available.

The RT version of the tablet uses an ARM microprocessor; that’s the same architecture favored by Apple and Android tablet makers. Microsoft is still working on a version of the Surface that uses an Intel microprocessor and will run regular Windows software. The company is differentiating that as a “Pro” model and has said it will cost more than the RT version.

It’s interesting to note that this initial version of the Surface tablet will only be available directly through Microsoft – at its retail stores and through Microsoft online, but not through the vast network of physical and online retailers who normally carry Microsoft products.