They really aren't similar at all - and there's plenty of other MMOs to draw the same conclusion from. This isn't a traditional open-world MMO, if you can even call it that to begin with. This game is like Guild Wars. No monthly subscription, content add-ons being what drives their revenue to keep the world open. All game worlds being instanced with player numbers capped, open explorable areas outside of missions that not everyone in the game shares. Guild Wars was outstanding, and an incredible value for the cost over the 8 or so years they supported it. Destiny follows the Guild Wars approach. 20 bucks, 15 if you weren't crazy and bought the pack for both? That's less than 2 months of subscription fees for WoW. Count some of that cost towards the cost of development, and the cost of support; as opposed to having to pay for entry to begin with and still buy the expansion.