Actually standard def is $12.99!! HD is 19.99. (the standard def option is the little teeny box they apparently don't want you to notice on the left)
Either way, not a bad deal AT ALL!! I'll probably go the SD route to hold me over until the Blu-Ray comes out.
One thing though, how soon after it airs does it show up in iTunes? I've had to bit-torrent the new episodes for the last three seasons, and it's becoming a bit of a pain in the keester.