eBay, the well-known online marketplace, has a subscription service which is designed to help new or inexperienced sellers set prices for their items and to better understand eBay marketplace concepts in general. The service, called eBay Marketplace Research, provides eBay members, who subscribe to the service access to data, charts, and graphs, to help them determine the demand for products (or services) they are planning to offer for sale. eBay Marketplace Research subscribers can examine top search results within a category, or across the entire site, to find out what buyers are searching for. Using the various charts provided, a subscriber can find information on average bids per item, the number of completed sales, and more.
You may want to consider a subscription to this service even if you don't regularly sell on eBay. For a fee of about $10 per month it is an excellent service where subscribers track actual sales on a large selling venue (eBay), review analysis in various forms, watch developing trends, and apply results to quickly design, or adapt, their own business marketing strategies.