Katie Ledecky chose to defer her entry to Stanford University until after the 2016 Olympics in Rio de Janeiro.

For this bright young woman, that decision was a no-brainer.

Now she faces a more difficult choice.

Should she want to compete in swimming for Stanford, which has been her stated intention, it will cost her a lot of money.

Given what she did the last week at the world championships in Kazan, Russia, Ledecky almost certainly would be worth north of $3 million in endorsements leading up to Rio.

“She’ll be the top female swimmer going into Rio, the American poster girl, the woman most likely to bring home the most gold,” said sports marketing expert Bob Dorfman of Baker Street Advertising. “And not turning pro could cost her around $3 million to $5 million in endorsement opportunities between now and Rio.”

Ledecky, 18, and gymnast Simone Biles, the two-time world all-around champion who recently turned pro, likely will be the most promoted U.S. athletes – by NBC and others – heading to next August’s Summer Games, even if neither can make the Olympic team until the U.S. trials in July.

“It doesn’t matter that (Ledecky) can’t qualify until July,” Dorfman said. “Marketers would jump on her anyway.”

Ledecky set her third world record at the championships Saturday to win her fifth gold medal of the meet. This one was in the 800-meter freestyle, in which her time of 8 minutes, 7.39 seconds broke her world mark from 2014 (8:11) and gave her the largest winning margin (10.36 seconds) in the event in world meet history.

“It’s almost to the point where I’m not surprised,” her coach Bruce Gemmell said. “She’s such a beautiful natural swimmer.”

In a 24-hour span, Ledecky set back-to-back world records in the 1,500. As if that wasn’t impressive enough, she returned the next night to win the 200 against a stellar field.

“We laugh about how she’s going to retire some men in this sport continuing to swim that fast,” said Frank Busch, U.S. national team director. “She’s doing things that are unprecedented in our sport.”

Such utter domination has sent expectations soaring for the recent high school graduate from suburban Washington, D.C., who has yet to even get a driver’s license. Ledecky remains oblivious to it all.

“I kind of try to keep the same mind-set I had going into 2012 – no expectations, no pressure, and whatever happens, happens,” she said. “I know my family and my coaches will all help me maintain that mind-set.”

If she were a pro, her victory in the 800 meters would have been worth $50,000, which includes $20,000 for the victory and $30,000 for a world record.

After becoming the first swimmer to win four individual freestyle golds at a single worlds – in the 200, 400, 800 and 1,500 – Ledecky’s overall haul in prizes and record bonuses would have been $172,500, presuming the relay money was split equally among all eight swimmers who competed for Team USA in the 800 freestyle.

NCAA rules do not allow swimmers to accept prize money for competing in the event. Expenses are covered by USA Swimming. That also meant Ledecky could not keep approximately $100,000 from her performance at the 2013 worlds – two world records, three individual golds and one relay gold – when prize and bonus money was about 25 percent lower.

As of now, the money Ledecky – and any other NCAA-eligible swimmer – has won at worlds would go to USA Swimming, which uses it for general funding and services.

The NCAA does allow athletes to take money earned in the U.S. Olympic Committee’s Operation Gold program. The Operation Gold reward is $25,000, $15,000 and $10,000 for gold, silver and bronze at the Olympics.

Ledecky’s U.S. teammate, Missy Franklin, faced the same choice in the lead-up to and aftermath of the 2012 Olympics, where she won four gold medals (two individual) and one bronze.

Franklin wanted to swim in college, and she did for two years at the University of California, turning pro after her sophomore season ended in March. She signed with WME/IMG, a megastar sports and entertainment agency with global clout, and then inked a contract with Speedo.

Her delayed decision to go pro, which Franklin has repeatedly refused to second-guess, may have further financial consequences. She will not go to Rio as the next big thing, the way she did in London in 2012.

Franklin, battling a back injury, left this year’s worlds without an individual gold. She won three, plus three relay golds, at the 2013 worlds, worth about $60,000 she could not keep.

“Now the swim fin’s on the other foot, so to speak, and it’s Ledecky who’s the fresh, new personality for the media and public to embrace,” Dorfman said. “She’ll be the big story leading up to Rio, while Franklin will take more of a supportive role.

“But Franklin will be a pro, and Ledecky apparently won’t. So a good deal of the $3 million or more in endorsement opportunities that Katie will miss out on could end up in Franklin’s bank account instead. Missy is a very appealing personality, still young, and may have more chances for gold in the 2020 Games. Ledecky should turn pro before 2020 and could cash in there – or will yet another U.S. swimming darling emerge by then?”

Whether she cashes in or not, Ledecky is simply focused on 2016.

“After (the 2013 world championships in) Barcelona, I set my goals for these last couple years, and I have a little ways to go still,” she said.

“I’m chipping away at those goals, and this is a really great steppingstone toward Olympic trials.”

The Associated Press contributed to this report.