Some info on what has changed in Xcode 4.3. Latest is 4.4 but a lot changed in 4.3 making this a good reference point.

Downloaded the XCode app, but not executed, the file system looked like:

  29G    /
5.0G	/Applications
2.5G	/Library
  0B	/Network
3.1G	/System
4.0K	/User Information
280M	/Users
259G	/Volumes
2.7M	/bin
  0B	/cores
4.5K	/dev
4.0K	/etc
1.0K	/home
7.8M	/mach_kernel
1.0K	/net
 17G	/private
1.5M	/sbin
4.0K	/tmp
360M	/usr
4.0K	/var

Executed /Applications/Xcode.app and installed command line tools:

 29G     /

5.0G	/Applications
2.5G	/Library
  0B	/Network
3.2G	/System
4.0K	/User Information
405M	/Users
259G	/Volumes
2.7M	/bin
  0B	/cores
4.5K	/dev
4.0K	/etc
1.0K	/home
7.8M	/mach_kernel
1.0K	/net
 17G	/private
1.5M	/sbin
4.0K	/tmp
453M	/usr
4.0K	/var