Asus selling millions of PCs a year that each pester their users to make a Microsoft account is well worth a major discount to them than any sort of additional OEM licensing revenue. Giving Asus cheap licenses lets them sell cheaper units to more people.

And yeah, Asus DOES need to sell windows laptops because the market demands it, but it doesn't mean they need to follow all of Microsoft's rules/goals. ("Pleeeeease put an NPU in every laptop and advertise copilot for us, pleeeease") Giving them a steep discount gives Microsoft a lever to pull if they feel like punishing an OEM later, though with the goal of avoiding anything that halts the sale of PCs with windows on it, which is bad for all parties.

You can't really model that on a supply/demand curve. Microsoft supplies Windows licenses, but Asus supplies a big chunk of market access. A license to software is an infinitely available resource which only has a value determined by the market's willingness to pay for it; a market that microsoft has historically been dogshit at accessing themselves. (Surface product line, for example)