I'm normally a huge fan of ShopItToMe.com, the amazing daily e-mail that categorizes when all of your favorite brands/sizes/ect. have gone on the red lines, but sometimes it's amusing (and almost annoying) to see how much the price on a single item can vary.
Take, for example, this laser-cut shift dress by Rebecca Taylor. It's $245 at ShopBop, and $210 at CUSP.
Or, you could go with this super-cute navy blue dress by BB Dakota, a mere $78 at South Moon Under.
Also, remember that it pays to check your local discount stores like Marshalls and TJ Maxx. I bought this Alice+Olivia number (it's from the Fall 2007 collection) way back in May for a mere $127. Here it is, on Singer22.com, for $150.
Same deal with this Catherine Malandrino dress, still $346 at ShopBop. It's definitely around $100 at TJ Maxx.
Lesson for the day: If you shop smart, you can buy more.