I doubt the "hype" over mechanical keyboards will be short lived
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People are still using the original IBM mechanical keyboards (with the large Din plug, let alone the later PS2 versions) after something like 20 years
A mechanical keyboard has a very distinct feel to it which some people absolutely love as it gives a much more precise and consistent indication of the key being pressed, and that's before the normally much better overall build quality, and the fact that it's proper switches rather than membrane tech tends to mean the keys themselves last much better.
About the only real reason mechanical keyboards "went out" was because of the cost of producing them - it costs pennies to put in a membrane keyboard layout (and the entire "switch" of that layout probably costs less than two or three mechanical switches), and people didn't want to pay large amounts for the keyboard when they could get a one for a fiver.
If I could justify the cost I'd probably get a good mechanical keyboard, as I used an IBM mechanical keyboard for a while and loved it, I regret not picking a bunch up in the late 90's when it seemed every computer fair had boxes of ex office keyboards cheap (especially as I now know how easy it is to clean the baccy stains off them).
Ultimately "mechanical" keyboards these days are a niche, performance type item, much like not everyone is going to want the latest greatest dual core video card in sli, or water cooling, a good case, or a good monitor, there are people who are willing to pay for the quality and feel of the product.
Oddly enough the keyboard/mouse and monitor are probably the three things I never stint on when building a machine for myself (and i never stint on a case when i build for anyone), as they are the bits you are going to be interacting with every single time you use the PC. thus if you can find one you like, as an enthusiast/heavy PC user it's nuts not get good ones that you like, even if it does mean potentially getting a slightly lower end video card, thus for me £60-100 for a keyboard isn't silly if it's comfortable