But the simple truth for all those decades is this: When there's already cat-whatever cable in the wall, it generally still works.
Decently-installed conduit (ie, actually-usable conduit) adds a ton of time and expense, which is why it is very seldom used for data circuits in residential structures.
The cable that exists is a lot better than the conduit that doesn't. And copper ethernet is bog-standard like MP3 is: It isn't the best in any technical sense at all, but everything supports it. Universal compatibility is pretty nice.
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So the ongoing cost of copper 10gbe is electricity. Someone else here in the comments says that a copper 10GBe SFP+ module can use ~3 Watts, or that a newer one can use about 1.5 Watts.
We can be generous by using the larger figure of 3 Watts, and 8 devices..
With 4 ports, eight 10-gig endpoints @ 3 Watts each, and $0.19 per kWh [delivered]: That's $3.28 per month, or about $400 per decade.
If we assume 1.5 Watt endpoints, then that number halves.
If we subtract the power consumption of fiber SFP+ modules (or media converters or whatever) to make the number a relative comparison instead of an absolute, then that figure goes down further.
Not so bad, compared to conduit.
