Yes, the "image in my mind" and what I would presume a gold case to look like, when someone says that, and knowing it has to be mostly space inside to fit things, and from drawings, led me to that type of dimension, which, to me (no expert) looks not a million miles off.
However, I must admit, I am still guessing. And there is a chance I will say, wow, I never expected it to be made that way.
I don't mind being wrong as I accept it's guesswork to a degree.
One thing I will say. There does seem, in other photo's to be another material in there.
If you imagine you have the computer part, this is then fixed to a module, a bit like an internal case, and then this fixes into the outer gold case.
Until we see it apart we don't know, but there is something else inside there, frame/support wise.
This picture will probably explain things easier than my explanation.
As you see, the "Case" may not actually be quite what we think, and you can see there is a lot of something else in there holding it all together, inside the "case" perhaps offering strength and support to the case, which may (and I only say may) contain less gold than Apple's statement could lead you to believe:
See what you think:
Image