They are selling emotes. Emotes. You know? Those optional things that you can buy to spruce up your character. The key word there was optional. Nobody is saying "Well, in order to continue playing Destiny you need to purchase X amounts of emotes." No one is saying that. They just saying "Here are these emotes. They are optional. You can purchase them if you so choose. If not, then don't buy them." They are not selling power, they are selling things that will determine what motion your character will make when you press a certain button.
Carry on.
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If this leads into an in game trading feature then that will be awesome.