The High Flyers and Trim & Grows are the most expensive but they're currently ridiculous on ebay. The most I have ever paid for any DB is $68 (a Trim & Grow). They yellow terribly and almost never come with all their plugs.
The ones I see the most of seem to be the Rainbows, and the purple MGR type. The orange and blue sparkly ones seem to be fairly common too. I got all my sparklies, rainbows, and MGR's under $40, with the majority being right around $20. The rainbows are prone to yellowing and their paint can rub off really easily. The perfume ones aren't too terribly uncommon, but it seems you only ever see the 2 blue ones or the paint is all messed up on their medallions & legs. None of mine cost over $50.