I think, like many things, people like the look but not the price. There are SO many knock-offs that are silver and with gem stones but much cheaper so people buy those.
What I smile about are those who buy the knock-offs, love the style and then say "Oh, I don't like the style of DY". Then why are you wearing that bracelet ring that is an exact COPY of his design?
Because they have no clue who he is. And that's the point....people are looking at the PRICE not the name and don't know the history about the design. Among younger consumers, names don't impress them.
There's an interesting article about Tiffany's and how they are addressing this issue (which, IMHO, is going to ruin the brand in the long run).