I think they are worth it. When I was researching on here someone mentioned about "..it's the interface to your computer blah blah blah..." It made sense, I do not regret my purchase in the least.
I did instantly get faster typing speed, not that I care much, but it is a bonus.
I paid a fair amount for mine because it had to have back-lighting, I did not want to purchase a premium keyboard that was not back-lit. If you do not care about back-lighting, as others have mentioned you can get a decent plank for around $80.
Think of all the money you spend on parts you never touch. You already have a performance machine, why not add a leather interior with a Momo steering wheel? It adds some comfort and class although it does not stick to your ass.
It is literally one of my favorite accessories I have ever bought for my computer. It's been weeks and I still wake up excited in the morning. lol
My Ducky goes "Clack clack"