See bottom of post for update.
Sergio Rossi's platform slingbacks retail for $695 at The Shoe Box.
These platform pumps by Steve Madden vary slightly as they have a wooden platform/heel but the shape/style is otherwise incredibly similar. They retail for $99.95 and you can click on the photo below to purchase.
*Update - 8/1/10* - Bebe now has a great look 4 less of these Sergio Rossi heels, available in blue, pink, or black. They retail for $149 and you can click on the photo below to purchase.