A system and method for providing a user interface to facilitate the purchase of unique items by presenting past purchase information of unique items to consumers. The user interface is a two-dimensional chart, with each axis of the chart representing a variation of values of an attribute that characterize an item that was previously sold. The system populates the chart with sales data that reflects the past sales of items having attribute values that fall within the chart. By visually presenting to consumers the distribution of past purchases, the consumer is better able to assess whether an item that they are purchasing falls within “typical” purchase behavior of other consumers. In some embodiments, the system allows a user to select a region of the chart and initiate a search for items that are available for purchase that satisfy the attribute values that are associated with the selected region.