Those are auction-site prices, not OCUK, right? But I think you're underestimating the home environment. Take the example of two professional adults at home with a WSE 2016 box or NAS elsewhere in the house backing up their PCs and handling WSUS, as well as central file storage.
Even my own home setup here requires three switches.
Don't be silly. For example, my brother works on Excel spreadsheets that run into the tens of gigabytes; the largest suite was over 100 GB. Even with gigabit ethernet those take a LONG time to transfer; with 10 gigabit, the time is reduced significantly.
He isn't right now because he doesn't have 10 GbE. He uses an external USB 3.1 drive.
But there are also thousands of people like him, just in the UK. Now scale that up worldwide.
So I'll bite! Why don't you spec up a 10 Gb Ethernet network for four people? Two adults and two children. Everyone has their own PC, the adults in a shared study and the children in their bedrooms, and there's a HP Microserver. The server is distant from the PCs but local to the internet router. From the internet router to the study is 30m and the bedrooms require an additional 10m or so each from the study. There's also a printer in the study with a gigabit port to be connected to the LAN. All kit is to be brand new.
Put up.
Actually, it's a combination of two real scenarios. So you can take your 'discredited' and discredit it.
I bet they said that about gigabit ethernet too. You'll note that high-bandwidth wifi routers are increasingly popular as long as they're cheap. Speed sells, but the price has to be affordable.
So please, get off your high horse and ignore why someone might want it and try to answer the question of why 10 GbE is still so expensive in the first place.
I started on 300 bps and 1200/75. I tapped 5 Mb thick ethernet. I strung 10 Mb ethernet BNC cables. So, please don't try that with me. I've seen networking go through several life cycles. We're more than overdue for 10 Gb to migrate from the datacentre to ubiquity.
If it were cheap there would be demand.
That's lovely.
I think a better choice would be this board. Okay, it's X470, not X570, but it has IPMI and onboard dual 10 Gb ethernet and auto-splits the x16 slots. Or this Epyc board.
You might also consider this build instead:
Very nice. I'm thinking of adding a dedicated fileserver and relegating my Microserver to Domain Controller, client backup, and WSUS.
What made you choose this board over (e.g.) the X10SDV-12C-TLN4f? That has 12 cores and onboard 10Gb Ethernet.
That was a bargain!