Mac OS X Lion - Xcode components simulator location
Solution 1:
In XCode5 the simulators are downloaded in a temporary folder download-and-install-cache-dstroot:
/private/var/folders/mb/yf1qy9bx7wg5dl01lzkvbytm0000gp/T/download-D39FB382-2540-4F2E-B8EC-6940A468CEAE-7723-000031655DACE7B0/download-and-install-cache-dstroot/Xcode.SDK.iPhoneSimulator.6.1-6.1.dmg
And I bet the simulator is linked to the compiler in a way that you need a new iOS6 simulator even if you had one for XCode 4.5.1.
Use Munki and Reposado to roll your own if you want to save downloading for each Mac.
Solution 2:
The download location changes every time you start the download.
find /private/var -name Xcode.SDK.iPhoneSim*
will reveal the download directory.
The download is restarted every time you click "Install", that is, any previous download is discarded (what a waste with 600 MB+ file size).
Although the downloaded file is a DMG, I still don't know how to copy from one machine to another to prevent downloading.
Solution 3:
The location of dmg file downloaded by Xcode is placed here.
~/Library/Caches/com.apple.dt.Xcode/Downloads