When Margaret Sherrod was in her 20s, she filled her weekends with 10k and other races, but in recent years she has cut back her competitive running schedule.

The 58-year-old retired teacher from Millersville is still in great shape and runs regularly for fun and fitness with a group called the Pacemakers. It's the cost that has dampened her love for races. She is now selective about which ones she participates in — the more expensive events can cost $100 or more — and chooses to run only a few a year.

"The price has escalated beyond belief to me," Sherrod said. "I love running, but I look at the price at the end of the day and I've decided I really don't need to race that much. I don't think it's worth it to me to spend that much."

Runners once boasted that theirs was one of the cheapest sports. All you needed was a pair of sneakers and the road. No expensive gyms or equipment.

Now a good pair of shoes costs at least $100 and runners often budget for races as they would a vacation or other extravagant event.

Old-timers remember when race entry fees cost as little as $5. In 2011, the average price of the country's top 100 marathons was $89, a 24 percent jump from 2007 when it cost $72, according to a survey by Twin Cities in Motion and trade group Running USA. The average price of a half-marathon rose 27 percent to $65, compared with $51 in 2007.

The Baltimore Running Festival charges runners on a sliding scale, depending on when they register. The earliest marathon registrants who signed up in April paid $90, while those who wait until right before the race in October will pay $130. The starting price was $70 in 2004.

Driving the rise in registration fees is the increased cost to put together a race, organizers of racing events said. Races were once simple affairs, but are now complex events that are as much a social outlet for people as a competitive race. Today's races include a festival with live music, post-race snacks for runners and T-shirts made of the latest-developed fabric.

It will cost about $2 million to pull off this year's Baltimore Running Festival, according to Baltimore-based Corrigan Sports Enterprises, the management company that organizes the event. The event also includes a half-marathon, 5K and a kids' run (prices vary for each of these races).

Running organizers such as Corrigan Sports said many people don't realize all the parts — and costs — that go into a race. City permits, police to monitor blocked-off roads, timing chips, finisher medals and signs all cost money, they said. Corrigan Sports also buys every parking spot at Camden Yards and M&T Bank Stadium so people won't have to pay for parking.

"Just like anything, our costs go up over time and we try to minimize it as best as possible," said Dave Gell with Corrigan Sports, which also organizes the Frederick Running Festival and other races. "Sometimes we can offset it with sponsorships, and sometimes we can't."

Kelly R. Dees, who works with Charm City Run Events, which organizes about 73 races a year, said her group works to minimize increases in registration fees.

"There is no doubt there has been an increase in price," Dees said. "We try to analyze those prices and make sure they only mirror the expenses that are going up."

The price increases could also reflect the growing popularity of racing and the diversity of today's running population. In 2011, 13.9 million people finished about 25,000 U.S. road races, a 167 percent increase from the 5.2 million finishers in 1991.

Running was once dominated by ultra-competitive males. Women now fuel the growth, and while they are competitive, they also want a fun, social experience.

"I'm an old-school runner, so I won't pay a lot," said Ryan Lamppa, a researcher with Running USA, a trade group. "I just need an accurate course that is timed well. I don't need all the bells and whistles. But I'm not the new runner. The new runner wants to have that festive, fun feeling."

The sport has also evolved into a business. A growing number of race management companies have cropped up as the sport has grown, and they all have to make a profit to survive.

"It has become more professional on the management side," Lamppa said. "There are more entities that are putting on races, and they are for-profit entities and their object is to put on a good race."

The more elite and popular the races, the higher the price. The ING New York City Marathon will cost runners who are part of the local running club $216 in 2014. Nonmembers will pay $255 and those from other countries $347. There is also an $11 application-processing fee.

The price of next year's Boston Marathon has not yet been decided, but those who ran this year paid $150 if they met a certain qualifying time, while nonqualifiers paid $300, according to the race's website.