Part of the cost? You mean the Beta? Well the Beta they needed to test their servers to make sure they don't crash on day 1, but it was also good advertising, yes. Like I said to another commenter, it's meaningless to us, but we are mere fans, and I think at Gamescom it's mostly other developers, sort of like E3, here. So basically its a way for developers, not just the ordinary fans, to say that they love the game. I think it's a pretty good sign - if the professionals are hailing Destiny, then it's likely they are praising it for subtle design choices that us non game-designers might not fully understand.