Microsoft has repeatedly told us that Windows 10 will be a free upgrade for anyone currently running Windows 7 or Windows 8.1. However, if you need to purchase a full copy of the OS (for building your own PC for example), there has been no official word from Redmond.
But on Saturday, Ed Bott of ZDNet wrote a story that a quick search of Newegg.com will give you the pre-order price for the new OS. It has Windows 10 Home listed for $109.99 and Windows 10 Professional for $149.99.
Another note of interest is it lists the release date of 8/31/2015 for the OEM system builder versions. Although, there is a caution symbol next to the date, so that could change at any time.
But keep in mind that other Windows OEM releases typically come about three months after the release to manufacturing (RTM) versions. So, if the information on this page stays consistent, it shows the gap has shrunk.
I went through and did a mock purchase, and was able to get all the way to checkout, so this looks like it should be the legitimate purchase price. Newegg is definitely a reputable online store, and when you go through the order process, copies are limited to 500.
This page might have been leaked prematurely, but, from what I can tell, has been up now for close to five hours at the time of this writing.