No, $10 for a cable with significant amount of power is unreasonable. If you ever dealt with some power cables, you'd know that 1 meter of the highest quality copper power cable for continuous delivery of say 15 amps (3 x 1.5 mm^2) shouldn't cost more than $0.6. And that's enough for 300 watts of power given 20 volts. But you probably will never see that much copper in a USB-C cable, at best you'll see third of that and with a flimsy insulation, which costs two orders of magnitude less than $10.

Power cords aren't that different - you can buy cheap and crap 6ft cords for $3 that won't last or you can buy construction-site worthy cords that get thrown around for $30+

Most charging cables get treated more like a power cord on a construction site - they don't just get plugged in and hidden behind a TV so the quality of the shielding and connectors is paramount to withstand the twisting and strains

Getting into anecdotal evidence here, but, as a consumer, I've seen what happens to the hyper-cheap cables after a few weeks to months of use: they tend to fall apart or fail in fun and interesting ways.

On the other hand, I have never had a $10-15 Anker or some other brand cable fail on me without serious abuse. As a consumer, I'll happily pay the extra few dollars for the expectation of durability, a warranty of some sort, and the knowledge that the cable should Just Work with most of my devices, even if I know that the price is way out of proportion to the materials involved.

Can't speak for all other consumers, of course, but I would expect that many have figured the same thing out over the years of purchasing Micro USB/Lightning/30pin/etc cables.

$1 for the 2m of cable, another $1 for plugs, $1 for manufacturing costs/packaging/shipping = $3. This results in a market price of $10 (30% goes to the retailer [amazon FBA fees etc], 30% goes to the manufacturer and these have to cover salaries, office space, tax, etc etc)