April e-commerce sales increased 15.6% year-over-year, according to MasterCard Advisors' SpendingPulse report, which also found the average price of an online transaction was up 0.2% compared to April 2009.   During last month, the luxury category posted a 15.5% year-over-year increase, paralleling its 15.2% jump in February. Electronics sales increased 8.5% year-over-year in April 2010, while women's apparel saw a 4.1% decline and men's apparel dropped 0.5% during the same period.   “The recession has been e-commerce's best friend,” said Fiona Dias, EVP of strategy and marketing at e-commerce firm GSI Commerce. “If you look at [fourth quarter] 2009 for retail stores, retail started to cut costs. They took associates out of their store; they took inventory out.” She added that retail will eventually recover, “but not at the same pace as e-commerce.”   Mike Berry, director of industry research at MasterCard SpendingPulse, noted that “in many sectors of the retail marketplace, e-commerce is the only major growth sector.”   “The retailers who are growing are the ones who are growing e-commerce traffic,” he said. “Many of the drivers of the e-commerce space are pure e-commerce players. They don't even have a bricks-and-mortar presence.”