You bought Rapunzel on eBay cheaper then retail? Congrats! I went in store, just so I didn't have to order it from the Disney Store website.
I would not be discouraged about eBay prices for the other dolls yet though, they have not come out and sharks are just over-inflating prices to scare us. I would say don't buy from them over retail prices until the fat lady sings. I think Belle and Ariel will be the hardest to get, but if you can go into a Disney Store, I think you might have a pretty good chance. Or even if you set an alarm for the website release. Rapunzel is still available on the website, and I think she is one of the more popular princesses in the set, and Snow White took two weeks to sell out. Last year for the villains, I just set an alarm for 3:00 AM (I'm on the East Coast) to get the Villains and I had no problem... granted, those were much higher edition sizes, but even if you look at the 17" Ariel that is coming out. She sold out within twelve hours, but if you go on right away you will have a pretty good chance of it! Best of luck to you trying to get Belle and Ariel!
EDIT:
Whoops! I didn't read that it was the original designer line you were talking about. Yeah... Belle and Ariel are up there, which is heartbreaking. I'm a Sophmore in college, so it basically becomes a game of "do I want to eat for a semester, or buy an Ariel designer doll..." You would be surprised how often I lean towards the doll... haha!
But I've seen them pretty low on eBay before. The lowest Belle I ever saw went for around $150? And Ariel I saw one the other week for $200 and I almost bought it, until I read that it didn't have the COA... I was so upset! Otherwise, I've seen her go the lowest around $280, from my experience. Some day, they will be mine though!