Is buying mass quantities of Duffy merchandise solely for resale as common in Japan as it is in the US? I'm not a "local" to Disneyland and even I've seen someone in Downtown Disney, buying up a pile of Duffy ears with his AP (or possibly receipt-coupon) discount. The CM helping us (cynically) noted the man was buying them to resell. Folks online even sell some of the Duffy items in quantities of 10!
Buying US items from one of those resellers on eBay is very nearly as easy as buying from the Disney Store online, and Disney loses out on the profit margin they'd have from selling non-discounted items directly to the consumer.
I'm not arguing that anyone's wrong about wanting to keep Duffy exclusive. But in this day and age, it's incredibly hard to really actually do it, even if they have item limits. When you can buy a lot of 10 9" Valentine's Duffies on eBay for $194.90, I can't help but feel like one reason the items disappear from the US stores is because people are buying just to turn a profit. It's probably not true (at least, I like to think the majority of purchasers are buying for themselves or as gifts), but I can't help but think it anyway.