I am partial to Logitech keyboards, as a typist and not a GAMER, so I don't use mechanical keyboards (yet). I was wondering what makes one membrane keyboard cost $30 and another $60+? As an example, I am now using a Logitech K270 (a decent keyboard but not unified USB), and looking for another Logitech like the K750. What's in the K750 that makes it more than double the price?
With membrane keyboards a lot of it comes down to the "features" - Wireless, fancy programmable/media keys.etc.  Ignoring the super cheap and nasty ones, being more expensive doesn't mean it will feel better to type on.  In fact, my favourite RUBBER dome/membrane boards are the Dell KB212 and those ones with the ridiculously huge space bars - Dirt cheap but actually feel really good.

That said, mechanical keyboards are certainly not just for gaming, It's just that they are currently the next big "cool" thing AMONGST gamers.  I almost never game (unless occasionally playing GTA with a 360 controller or Minecraft counts) yet I use really high end keyboards as I spend hours a day typing (programming).  At home I use a Topre Realforce with capacitive rubber domes and at work I use a Filco Majestouch with Cherry MX Blue switches.  They are both great for typing (as are the several IBM Model Ms) I also use.  In fact, I'd argue that a good mechanical/high end keyboard is more important for a typist than it is for a gamer.  Just look for the high end ones and ignore the flashy light up "gaming" ones that promise nonsense about low lag. 

Sure they are expensive, but they will last a long time and can often be repaired if they go wrong, if one of the switches on my Filco died for example, I could pick a new one up for £1 and replace it.  For example, one of my favourite keyboards is an IBM Model M from 1986, it has been heavily used over the years but apart from being a bit yellowed, after a good clean it works as good as new!camerongray, thanks for the excellent reply. Myself being an ancient IBM desktop user, I am also very partial to the IBM model M keyboard. I noticed that they are still available, and I am definitely TEMPTED.

Happy Holidays,Yeah, the Model Ms are awesome - I have both a pair of original ones (From 1986 and 1989) and a more modern Unicomp Classic from 2012 - They all feel great!Unicomp Ultra Classic User here! Glad I got it before the Canadian dollar dropped hard... Buckling Spring switches are noisy but amazing to type with.

I have sort of the same perspective as Cameron here. The membrane keyboards I find least annoying tend to be the cheapest ones. I have two right now- a cheap Microsoft Wired Keyboard 500, and a wireless keyboard. The wireless keyboard was more expensive (even accounting for the mouse that came with it) but I can't stand it- they screwed with the key layout, it feels mushier than FRESH bread and is not nearly as tasty.

Usually more expensive keyboards that use membrane switches tend to add things like added media keys or backlighting features. This is similar for more expensive "gamer" keyboards- For some of those you find they provide full RGB backlighting that can be customized for every single key. Which is, uh... somehow useful, I guess?