SHARON TANENBAUM has been a serious runner for six years. The Brooklyn resident, 30, has completed three marathons and several shorter races. Each week she logs about 20 miles.

Her favorite trainers? A $25 pair of Champion shoes she bought at Target.

“I like running in simple shoes,” she said. “The more you pay, the more unnecessary stuff you get.”

She is right. Money often buys higher-quality goods, but not when it comes to running shoes.

Over the last three decades, running has exploded as a leisure sport. In 2009, 476,000 runners completed a marathon. In 1976, the number was just 25,000. Sales of running shoes reached a record $2.36 billion in 2009, 60 percent more than a decade earlier.

But some of those dollars may not have been well spent. In 2007, Scottish researchers tested running shoes at three price levels, ranging from $80 to $150, and found that low- and midcost shoes within the same brand cushioned runners’ feet just as well as high-cost ones — sometimes even better.