It looks like you're new here. If you want to get involved, click one of these buttons!
The inital download is around 3.4 gigs, then probably at least 2-3 gigs of patches.
My folder is 5.46 gigs fully patched.
I just checked my fully functional Beta install and it's sitting at 3.67GB.
If you have 5-6GB it might be because you're keeping the setup file in the same folder, but that's not necessary to run it.
My opinion is my own. I respect all other opinions and views equally, but keep in mind that my opinion will always be the best for me. That's why it's my opinion.