A few days before New Year's, my daughter came upon the free iPad app for the Furby Boom and fell in love with the toy. I usually do not fall prey to her whimsical wants, but with her 6th birthday approaching, it seemed like good timing to buy the toy, which is an interactive stuffed animal that responds to human voices and commands from the app. I thought I could pop into a discount chain and pick one up on a post-Christmas sale. Then I learned that buying a Furby Boom was like playing the stock market. The roly-poly fuzz ball, which is the latest iteration of a craze that started in 1998, sells out at most stores. It trades online at a premium high above its manufacturer's suggested retail price of $59. Since November, retail prices have fluctuated from a low of $29 to more than $100. When is the best time to buy a Furby Boom? To figure that out, I assessed price data to identify the timing of the next sale. Experts have access to up-to-the-minute price and inventory