Sell, who now works as a scientist in the bio-safety division of Lancaster Laboratories, pointed to another trade-off: Years spent competing are years not spent climbing the corporate ladder, or learning new skills.

"If I had put the past 10 years of work and intensity into anything else, I would be much further ahead financially than I am now," Sell said.

When the Olympics don't call

Olympic glory itself can boost athletes' income. Americans who win gold medals in London will receive a $25,000 bonus, while silver medals will bring $15,000 and bronze medal winners will net $10,000.

But some elite athletes won't even get that far. Consider the case of Ben Bruce, a Californian who specializes in the steeplechase, an odd event that requires contestants to jump over hurdles and a water pit during a run that measures just less than two miles.

Bruce failed to qualify for the London Games at the recent Olympic Trials. He needed to finish third in the event final, but faded to fifth. The loss puts him in the unfortunate position of being one of the sport's best athletes to not make the team.

"There are a lot of us that are technically living under the poverty line," Bruce said, referring to a period between 2008 and 2010 when he had no sponsors. "In this sport, nobody is looking to give you a free ride."

"When I would file taxes at the end of the year, I was not making more than $10,000."

Yet Bruce isn't ready to hang up his spikes. After several tough years when he worked delivering pizzas and cleaning houses, he has picked up an Adidas sponsorship, and is now working with a training group that helps to defray the cost of competing.

The 'other' sports

While a money-earning hierarchy exists within the insular world of track and field, there are also vast differences among sports.

Basketball players, for example, make millions in the NBA, and yet will walk into the Olympic stadium next to lower-earning athletes from other sports that, despite their relative obscurity, require significant investments in equipment, training and time

Scott Parsons, a 33-year-old Maryland resident, is scheduled to compete in the kayak slalom event in London. It will be his third trip to the Olympics.

Kayak athletes don't have the same sponsorship opportunities available to track and field athletes. "It's hard," Parsons said. "I think a few people are getting some money here and there, but it's not much at all."

To make ends meet, Parsons has worked part-time jobs, including one at Walter Reed Army Medical Center. He also estimates that he has lived in five different basement apartments over the past 10 years.

But Parsons is content with the path he chose.

"This is the kind of sport that you do because you love it," Parsons said. "I'd be doing this sport whether it was in the Olympics or not."

A professional movement

Nelson, the shot putter, described the financial hardships faced by athletes today as a continuation of a decades-long battle to be treated as professionals.

The disputes date back at least back to Steve Prefontaine, the long-distance runner of the 1970s who famously thumbed his nose at the constricting rules of Amateur Athletics Union and the NCAA, which forced him onto food stamps.

"I don't think anything has changed," Nelson said. "I think Prefontaine was one of the first people in this country to see the system for what it is."

As evidence, Nelson pointed to the lucrative television contracts, and the evolution of the Olympics as a major-league business -- with little noticeable benefit to athletes.

"All kinds of people involved in the Olympics are making a lot of money off the hard work of athletes. And those people don't have to pay our salaries, and that is a shame," he said.