I was going to try out a setup with a stationary desk mic like
@Josh | NFC was saying his friends tried, but apparently that might not be the way to go!
I really recommend this setup, because you essentially stay tether-free as you are in no contact with the mic itself. I have wireless Sennheiser headphones and a desktop mic. It is a wonderful way to go But make sure to have it on an arm, or every single vibration caused by moving the mouse or typing will be heard.
But back to the topic: Sure, engineering costs, but enginreering cost a lot also before, but still some things were cheaper (e.g. my MX518 example above). I think it much of the price is just increase of profit margin, because they know the customers will pay for it. As you said: people are jumping on trends, and are ready to pay for it without thinking about what they are paying for.
I myself was sooo close to buying a racing chair, until I had the brains to first go out and try them out and realize that they are the worst back-killers ever brought to the market with 0 ergonomy.
But like the gaming industry, where the common excuse for DLC is that it cost so much to develop games, what is ignored in those discussions is the fact that these days, there are so many already made libraries, so devs do not have to develop everything from scratch. There was also a video that discussed this, and came to the conclusion it is no more expensive, and in some cases cheaper, to develop a game than before. And then furthermore, the customer base is far greater than before.
And that last thing is a point I want to expand on for the engineering-argument; Even if it costs more in engineering, they also have a lot more gamers that will buy nowdays. And the annual engineering improvements are usually not that much. It is the brands that release models every 5 years or so that are actually doing engineering stuff.
Anyway, I still believe that in the end it is like you said; it is all about trends, companies catering for those trends, and end-users falling in line for those trends without thinking enough about it.