Note that this has nothing to do with us not wanting to throw in $300 for airfare. Rather, it has to do with us not being able to legally put ourselves in a position of providing international travel, visas, passport clearances, and all of the other fun stuff necessary in a contest involving transportation.
Our choice was simple - either have the grand prize require travel to our HQ (which is the same offering requirement as last year's grand prize), or to restrict the grand prize to members in the USA, only. We chose to keep it open to everyone.
That said, the Grand Prize winner will still have their choice of any other prize if they so choose - which, I believe I can firmly say, blows any other contest that we or anyone else has ever done out of the water.