So you've made a sale. Whew! The hard work is over.
Customers are great. They make up a huge segment of the buying population, but we make games. We don't need just customers, because odds are you'll never reach enough people to survive selling just one booster pack, starter set, or game (unless the game's really expensive...still, you're not making those expansions for your health!)
Just like Tourists, you have to treat you Customers right. In fact, the very fact they've put down some hard earned cash means their attention is focuses squarely on you, what you are selling, and how you support it. Unlike Tourists, customers really care about what they're getting. They've put their toe in the pool and now it's up to you to make sure it's the right temperature.
If it is, some of your customers will become what you really want. What you really need. They will become FANS.