DIY
Ask the seller at cube4you for a price if you're ordering more than one cube. I ordered 5 cubes at a rate less than US$6.50 each
Also, make sure you pay attention to the description or name. I think there's 3 classes of DIYs at cube4you. A, B and C. A being the best I assume.
4x4x4
I've Rubik's Revenge which is nice and loose, in contrast to the Professor Cube. It turns well enough. I think I have the e4 version of the East Sheen 4x4x4 which turns well too. A notable difference between the two is that the East Sheen is smaller and lighter. NB: I bought an m4 and for some reason it jammed during turns like "r" or "l"
A4 - DIY Already Assembled
K4 - DIY Kit (Not Assembled)
E4 - DIY Already Assembled (plastic packaging)
M4 - DIY Already Assembled (dome packaging)
A4 and K4 are exactly the same according to the site except for the fact that A4 isn't a "KIT" per se.
It seems that they're all the same except that each is in a slightly different packaging and one isn't assembled.