A lot of people can calculate ROI, but manufacture's resources are limited. Therefore it's out of stock worldiwede. I suppose that all x11 vendors product ~100-500psc per month, that purchased immediately by big miners.
I'm just getting in to this (my first couple of days) and i would suggest not.
I have a Windows 10 gaming machine, i7 6700k,16gb ram, triple monitors, 48tb disk and ..... a Zotac 1080 EXTREME O/C edition card and I can only get about 14MH/s. From what i've seen, this is pretty rubbish. As i've said though, I am brand new to this and so there may be configuration options i can do to change this but, as it's also a gaming machine (that mines in it's spare time) i don't want to do anything too drastic.
I think most people setting up dedicated PC solutions go for multiple AMD cards, could be wrong though.
Sadly, i really do think we just have to wait for new ASICs to become available to do it at a relatively cheap price.