While Machine Learning is one of the most popular research areas in Computer Science right now, there are still only a few applications meant to be used by the general public. We propose to develop an exemplary application that can be directly applied to eBay trading. We would like to build a system that predicts how much an item would sell for on eBay based on that item's parameters; we intend to run our experiments on the eBay laptop category. Prior trades will be used as training data. The system will implement a feature-weighted /k/-Nearest Neighbor algorithm, using genetic algorithms to determine feature weights.