What is the installation size of a clean build of 4.2? This is a pretty simple question, but one that I have not been able to find the answer to.  How much disk/storage space does an installation of Jelly Bean (bonus points for other versions) take up?  I am not looking for a super-accurate answer, as installation size varies from device to device, but more of a ballpark answer in the gigabyte/gibibyte range, such as 1.7 GB.  Or does Android's size vary drastically from device to device?
Well, to put this another way:

For Gingerbread, storage space weighs around 95Mb, give or take, including Google Apps, source code 6.5GB, compilation taking up approx 14GB space.

Android's storage space for ICS, weighs around 160Mb, give or take, including Google Apps, source code 9.5GB, compilation - takes up approx 20GB space.

As to JB, have not yet built it, but source code is 12.5GB, compilation takes up around 25GB space, various official JB images hovers around 200Mb mark.

The above ball-park figures above, reflects from GB, ICS and JB. As for the future versions of Android, only time will tell how much more space will be taken up, it will increase, no doubt!

As for the final image build output, this would be dependent on handset, as ROM developers/manufacturers love to add their own bits, hence the inclusion of the "give or take" in the above sentences, not to mention carrier bloat-ware so the mileage will vary.