Spend 10 minutes in any of the many stores at WWOHP and try and add up the total of several transactions. That merch is gold, whether they're selling them at WalMart or not.
In fact, because it's NOT sold at WalMart, people are more apt to buy. It's unique and special.
Have you ever been to Tatooine Traders when there wasn't a line? Ever seen the mega-lines at the huge merch tent during Star Wars Weekends?
That's even with most of the same merch being sold at every big retailer (and for a lot less $$$)!!!
Besides, just wait until SW has its own "land"...