For what I photo.. Yes big difference... Probably not £7k but £3.5k I paid yes
The ISO is miles better and as I photo in dark places that alone makes it worth the money
However I have found some very annoying things about the camera
I can only get the full frame rate advertised when shooting at f2.8 the bigger the fstop the slower the frame rate... Even holding down the backbutton and focusing effect it.. The above happens slightly wiht the 1dx2 but more prominant with the 3... doesnt seem to happen at all wiht the 1dx.. Its very annoying
I dont know if this is because I am using an older 400 lens and not the latest... But as mines tack sharp I aint upgrading
The recognise focus system is good for certain jobs such as when i shoot dogs, boxing or any single person sports.. not good for field sports as you cant predict which player its going to fucus on..
the touch scren is pretty useless for me as i am always wiping the screen haha i dont see any advantage..
theres a few other extras on the camera that i dont find usefull at all.
VIDEO I dont use but i dod try it out... its got stabalisation and i can walk around a room and take steady video hand held
All in all for my needs its worth it.. but its not perfect IMHO