The pricing difference is part of the product segmentation, because 10G+ has been reserved for "enterprise" parts despite not being much different at this point. There are ARM SOC's out there, where the bare SOC is in the $40 ballpark and comes with 10G integrated. 10G isn't inherently more expensive, its just been a decision not to repeat the "mistake" that was the 100-1G transition where the price went from $$$$ to 1/10$ in the space of a year.
I don't understand what we are talking about. None of the CPUs in this article have integrated NICs. The NIC is a little pea-sized peripheral device on a PCIe port. If the motherboard makers thought anyone needed a desktop platform with 10gbe, they'd ship that. But 10gbe controllers cost a lot of money and draw a lot of power, and take more pci-e lanes. I think they are banking on the idea that people who want it will be happy enough with expansion cards or thunderbolt peripherals.
A 10G port takes the same PCIe lane as a 1G port, particularly if you have PCIe gen4+ or are willing to potentially lose a bit with gen3. Similarly with power, EEE doesn't use the power if its not needed. Which for users on short runs, or with 1G switches the power utilization will be the same as a 1G port. And given that we are talking 200W parts, a watt or two for 10G isn't going to be missed.
And probably more of the motherboard manufactures would put 10G nics on board if there weren't a dearth of 10G pci nic chips from manufactures not already selling PCIe nics as high margin products. AKA intel selling its 10G part for more than the rest of the parts on the motherboard is going to keep motherboard manufactures from putting it on every motherboard.
Its sort of been a game of chicken, which will explode violently when the patents expire and a company like etron or asmedia starts producing them. (both of which have shown plenty of inhouse capability for producing high speed phy/etc interfaces).
I think you severely under estimated the cost difference in 2.5G/5G SerDes to 10G, and the cut throat nature of PC business, where $1 of BOM cost is a world of difference.
There is also the question of ecosystem like switches. The TCO of owning 10G is still pretty much out of reach for most consumers.
