“Wow, that’s a lot of money.”

It was the moment that confirmed to Sloane Stephens that her rise through the tennis rankings from 957th in the world barely a month ago to US Open winner was also a lucrative one.

The American’s 6-3 6-0 win over close friend Madison Keys garnered her one the most coveted trophies in tennis, a rise from No.83 to No.17 in the WTA rankings and a cheque for $US3.7 million ($A4.6 million).

“How insane,” Stephens said. “I should retire now, I told Madison. I would never be able to top this.”

BEST. DAY. EVER. 🇺🇸🏆 pic.twitter.com/R8ARc09Qwb

— sloanestephens (@SloaneStephens) September 10, 2017

“Girl, did you see that check that lady handed me? If that doesn’t make you want to play tennis, I don’t know what will,” Sloane was reported to have said on wta.tennis.com, with Keys keen to join the celebrations, adding “She can buy me drinks, all of the drinks.”

Stephens’ maiden grand slam title capped one the game’s greatest comeback stories having recovered from a serious foot injury to become the lowest-ranked women’s grand slam winner since Chris O’Neil at the 1978 Australian Open,

The 24-year-old finally broke through four years after reaching her first grand slam semi-final at the 2013 Australian Open.

“When I was 11, mum took me to a tennis academy. (They) said I’d be lucky to be a Division II player without a scholarship,” Stephens said.

Stephens’ mother, Sybil Smith, a swimmer at Boston University, became the first African-American female to be named First Team All-American in Division I history.

Her father, John Stephens, was a professional American footballer before dying in a car accident on the eve of the 2009 US Open.

Despite her pedigree, Stephens was the underdog in Saturday’s final against Keys, the hardest hitter in women’s tennis.

Yet Stephens not only returned everything Keys threw at her with interest, but also committed just six unforced errors.

Sloane Stephens with the US Open trophy. Photo: Getty

“Shut the front door. I don’t think that’s ever happened to me before. Oh, my God. That’s a stat,” the jubilant champion said.

“It’s incredible. I honestly had surgery January 23 and if someone had told me I’d win the US Open, I would have said it’s impossible.

“It shows you what happens when something you love is taken away from you.

“Madi is one of my best friends on tour and to play her here, I wouldn’t have wanted to play anyone else.

“I told her I wish it could be a draw and if it was the other way around she’d do the same. To stand here with her today is incredible, that’s what real friendship is.”

Both players sat out the Australian Open, with Keys herself needing two wrist operations to get back on court, let alone play Stephens, in the first all-American final since Serena Williams beat sister Venus in 2002.

“From what I’ve been through, if you told me at the start of the year I’d be a US Open finalist, I wouldn’t have believed it,” Keys said.

“Obviously I didn’t play my best tennis today and I was really disappointed, but Sloane was very supportive and if there was someone I had to lose to today I’m glad it’s her.”