Agreed, this is a lot different than a Pay Per Click (PPC) campaign where you're attempting to sell an app to people who expressed general interest such things. Click throughs on those do range between .5% and 2% then you have to deal with conversion to sale.
What are doing is marketing to a well developed highly dedicated fan base with a laser target product, the celebrity they are a fan of and an opportunity to see them live and interact with them. So it's an apples and oranges comparison. The conversion percentage should be huge.
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