The Estirator shows recent item listings from eBay Kleinanzeigen to the user, without letting him know the price. It's the users task to estimate a price for the items.
When the user submitted his estimations he gets access to a list of items, sorted by how much under worth they are sold.
Find super cheap offers within seconds.
Get an idea of how much customers would spent for your product.
Possible A/B testing for product photos and their influence on the customer.