While the actual purchase price of Windows 8 is lower than previous Windows releases, it seems Microsoft is using multiple ways to keep generating revenue from its upcoming OS, clearly inspired by other OS'es. Current Windows releases don't include Windows Media Center which has to be purchased separately and Microsoft also wants its share from another revenue stream: advertising in Metro apps.
Microsoft has used advertisements as a business model before, it included them in the Starter Editions of Microsoft Office.
On mobile phone OS'es it is common practice to include advertisements and Microsoft is now bringing the same experience to the desktop. To enable application developers to start experimenting on how to monetize their apps, Microsoft has released a Microsoft Advertising SDK for Windows 8. The SDK should help developers to easily integrate advertisements in Metro apps.
Metro apps will be a cashcow for Microsoft as they need to be installed through the Windows Marketplace, where Microsoft takes a 20-30% cut depending on the amount of sales. The advertisements will also bring Microsoft additional revenue as they are served through Microsoft's advertising servers for which Microsoft also takes an (undisclosed yet) percentage of the revenues.
According to the developer guidelines it is not allowed to use a Metro Tile as an advertisement but an actual application can include text, image and video advertisements with sizes ranging from 160x600 pixels to 90x728 pixels. Like on other systems, advertisements can be refreshed automatically and targeting to specific geographical locations is possible.
