Microsoft has yet to reveal how much it plans to charge PC manufacturers (or customers) for Windows 10. In the meantime, however, a new document published on the company’s OEM Partner Center site sheds a bit more light on how much it currently charges partners for Windows 8.1 with Bing.

Last May, Microsoft announced a subsidized version of its latest operating system dubbed Windows 8.1 with Bing. Offered only to manufacturers as a pre-install on new devices, the idea was to drive adoption of Windows 8.1 and Office on budget-minded systems.

As the document from the OEM Partner Center site shows, Microsoft offers Windows 8.1 with Bing to makers of small tablets (those with screen sizes smaller than nine inches) for $10. Factor in the configuration discount of $10 and we see that manufacturers don’t pay a dime for the OS.

Tablets with screen sizes of 10.1-inch or smaller (down to nine inches, presumably) are charged a royalty of $25 minus the configuration discount of $10 for a final price of $15. The same fees are charged regardless of whether or not Office 365 is included as a free bundle to buyers.

To be eligible for the configuration discount, Bing must be set as the default search engine and MSN must be set as the default home page on any included web browser. These defaults can be changed by the end user at any time. Furthermore, the offers only apply to x86-based devices.

Given this knowledge, it’ll be interesting to see how much Microsoft is planning to charge for Windows 10.