Thanks to the Internet, information about an artist's worth is at your fingertips. Going online and searching for results on number of tickets sold by that artist in your market is a great starting point. Pollstar provides ticket sales information, but only for venues, promoters, and artists that submit the information. A reputable talent buyer or agent should be able to provide honest information and stats about most artists. That information should include, but is not limited to, the last time the artist was in the market, what venue, ticket sales and that sixth sense of how a certain artist will do in the market.