Lots of great prices online. Be sure to check out parfum1, scentedmonkey, and beautyencounter before buying anywhere else. Ebay is good for frags that are not likely to be fake. I like to buy partial bottles at discounts on ebay, but those deals don't come around too often, especially now that I'm not really looking for anything (mostly do swaps).
If you're paying $50 for anything that's not a niche, you're not getting a good deal. I won't pay more than $40 for anything there, and it'd have to be a 100 ml bottle that I really want. If you're going $50 and up, you may as well get a fresher bottle from a department store.