If you preorder through Origin, it is literally an additional £5 (I'm in the UK)
http://buy.swtor.com/uk/
Note the part that says "Includes Origin £5 Pre-Order Fee"
Given that I could pick up this game on the 20th from ASDA down the road for £35 it's actually £10 I'm paying extra for the sake of this preorder.
Note: I'm not particularly fussed, I only came to this forum to see if there were any indication of when I can expect availability, but I noticed your post and thought I could be helpful