There’s a handful of people who will “buy the store out”, so they want to prevent this. I believe they should answer customer questions no matter what. Also, if they wish to restrict purchases, why not allow you to buy one of each design? That way you can buy whatever you want without leaving the store dissappointed (except for resellers or collectors who love multipules).
I strongly believe The Cosmetics Store and/or Estee Lauder don’t want you to pay discounted prices; they want you to pay full retail price. It’s like this store is Top Secret hush hush–nobody must know about it. On the other hand, if they don’t want you to get 10-30% off, they shouldn’t have created this option. It would be easier for them to just leave the solids at the department stores and never have a sale.