The work around for this, while probably not officially supported for obvious reasons (they want more money), is to change a registry key. This was posted for Windows 7 update keys doing the same thing on a forum (though I had an update version AND did a clean install MULTIPLE times without having to do this) but worked without an issue on my laptop running Windows 8 regardless.
1. Run the registry editor (regedit)
2. Find the following key: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup\OOBE
3. Change the value for ‘MediaBootInstall’ from 1 to 0
4. Open an elevated command prompt (run as admin)
5. Run the following command: slmgr -rearm
6. Reboot
If you already entered your key, check the activation: for me it was already activated and I needed to do nothing more. If not, type in activate windows and type in the key; it should work. Also, do yourself a favor and export this key from regedit and save it somewhere if you ever are required to do another clean install. I know I did.