The perception of lower prices at Whole Foods was enough for customers from a wide variety of chains to give the organic grocer a try. Trader Joe’s saw 10 percent of its regular customers visit Whole Foods between Aug. 28 and Sept. 16, according to Thasos Group. Eight percent of Sprouts customers did the same as did three percent of Target shoppers and two percent of Costco and Safeway customers. Kroger and Walmart shoppers were the biggest source of new customers at Whole Foods following Amazon’s acquisition of the chain.