The steep price I think is justified, as you get a very sturdy box, which also - despite only glued rings - a lot looks valent than a cheap plastic folding. It is held together by Velcro and for building one needs about 10 seconds. The box slides in fully loaded condition is not in the trunk around, but remains in place.
Dimensions (height / width / depth) in cm: Built: 19.5 / 48/33 Folded up (quite flat): 0.5 / 86/71 Folded up (to save space): 2.5 / 48/33
To get a rough idea of the size, I have a photo set on which the box in the trunk of an Audi A5 can be seen.