Yes i agree, there is no real cross reference here apart the fact we are keep seeing more and more RS that are quite capable in providing same results on cpu/gpu, it is more of a Bike vs car stuff, someone can go around the world with bike and someone can't drive to the store it all depends on many factors.
I can't discuss publicly but this retail price for 2680v3 processors is insane... cheapest i did find was 1400e so this was very good deal(no it didn't fall of the truck :))
I can't find titan-z(i was discussing them since those are the ones used for octane RS) for less then 1.5k i know titan-x will be killer and cheaper but when it gets out, right now price is big mystery someone is saying 1k others 1.3k.
It is matter of some time(years) when gpu(or some other form of more compact architecture) will take over, just 2-3 years ago you could fry egg on mid range gpu, now you have beast that don't even get warm(over exaggerating :))
I used and tried few of GPU RS they are not as nearly "flamboyant" types you are willing to jump in bed when you lay eyes on them for the first time, but when you get them home... :D More of a plastic fantastic types that keep their teeth on night table and garter belt they bought from Top shop... but they know how to talk dirty and sometimes it is exactly what you want, but they are dyslectic so do not expect them to read you bed time story...
I tried 2x780gtx and it doesn't even come close to let's say 2x4930k, i am talking not only one gpu/cpu RS but several tests. I don't have titans but 2680v3 is beast and Vray and Corona go well with it.
12gb is joke, it cramps style of(few months in project) i don't care anymore(yes when you are listening to Ramones), no one will be willing to be extra careful with texture size, meshes etc. so it could fit in 12gb of ram... I am sure that 99% of people would rather save few days there as they wouldn't have to clean scene meshes and different assets... and have those extra days for longer rendering(but it isn't).
Already saw those papers, they are quite old... Anyhow lots of new stuff is coming soon, nvidia is already failed to fulfill their promises(last couple of years) things are rolling slowly and i am sure CPU giant Intel wouldn't let P4 fiasco to happen again same as AMD claim to have ace in their sleeve for 2016.
Things weren't so openly secretive for quite some time and who knows what might happen, but i am sure in one thing that GPU isn't only thing right now that wants piece of cake.
I think it is more of standardization of industry that will win at the end, that is why you can see UE starting to take of, it is based on something old more or less standardized, usually to change things you need more revolutionary approach and for now i don't see anything else except Corona to do this(no this is not fanboyism) i hate the fact i have to learn new RS again, i hate the fact i had to spent 300e on another piece of software, i hate lots of shit but i have to take bow to Ondra(and puke on his new yellow later pattent shoes while taking that bow and thank him at the end) as standardization based on monopoly is worst type...
All this seems to me like i saw it before, oh yes i did...
Sorry ondra i puked on your new shoes i will buy you new ones next year :D