Microsoft has been aggressive about pushing Windows for low-cost tablets. Last April, it announced that the OS would be free to hardware makers building smartphones and tablets with screens smaller than 9". Now, OEM pricing information published by ZDNet's Mary Jo Foley shows the incentives available for slightly larger devices.
According to a screen capture from Microsft's OEM Partner Center, tablets with screens from 9" to 10.1" can be equipped with Windows 8.1 for only $15. The price of the OS is actually listed as $25 for those machines, but a "configuration discount" knocks $10 off the total. Tablets under 9" combine the same configuration discount with a $10 starting price, reducing the net cost to zero.
The specific version of the OS is Windows 8.1 with Bing, which makes MSN the default homepage and Bing the default search provider. Users are free to alter those pre-defined preferences, of course. Hardware vendors are also free to include one-year subscriptions to Office 365 at no additional charge. Tablets between 9" and 10.1" can get in on a variant of the suite designed "for tablets," while sub-9" devices are eligible for a "small tablets" flavor. Neither derivative is listed in the Office 365 version matrix, making it difficult to differentiate between them.
The discounts apply only to tablets, but Microsoft notes that a "keyboard may be included." Detachable convertibles presumably qualify. There's no mention of devices with screen sizes larger than 10.1". Larger tablets face less competition from systems running Android and iOS, so there may be little need for incentives. The situation could change if Apple's rumored jumbo iPad makes it out this year, though.