The designers know what the people like, and the heads want to build what the money-spending people (in this case, HP fans) will like, and Diagon Alley right next to Hogsmeade won't cut it. The heads know the designers are smart, and they are not going to make them draw up something that won't work, and a rediculously non-canon WW will not work.
I'll also remember this portion of the thread for how cocky you're being.
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Fan or not, everyone who goes to Disney spends money. There's no difference. But there is a big difference between how much money. The average vacationeer is not going to shell out $300 for a broomstick, $80 for a map, and $350 for a wooden cane.