Ebay is one of the first places I look when hunting for a piece that is either too expensive, exclusive, discontinued, or out of stock. For instance, when I first heard the news about the ever-elusive Miu Miu glitter oxfords (which are unavailable on Nordstrom), I turned to my good ole friend Ebay.
While you can often find things for a discounted price, you do have to be a bit cautious about what you buy. Look at all the pictures, seller information, and product details to ensure that you are getting what you think you are.
Some things are still a bit pricey, but when you think about their retail price it seems a lot less. I suggest finding a piece that you LOVE, and saving up for it. In a budget, there is a balance of splurges and savings. Just lay off buying clothes for the month and buy that amazing pair of Prada heels.