Kylie Jenner bragged about how "rich" she was to Jennifer Lopez and Alex Rodriguez at this year's Metropolitan Museum of Art's Costume Institute

Speaking to Sports Illustrated magazine, Alex explained: "We had a great table. The black guy from 'The Wire' --Idris Elba, yeah, and his new wife. Some famous singer next to me, I don't know what her name is. Versace--Donatella. We had Kylie and Kendall [Jenner]. And we had an Asian gentleman from 'Rich Asians', the lead.

"Kylie was talking about Instagram and her lipstick, and how rich she is."

Her cash confidence comes as no surprise as back in March the 21-year-old reality TV star was named the world's youngest self-made billionaire by Forbes magazine.

The brunette beauty - who has 16-month-old daughter Stormi with Travis Scott - insists she "didn't expect" to be so successful when she launched her beauty business Kylie Cosmetics, which Forbes magazine values at at least $900 million, four years ago.

She said at the time: "I didn't expect anything. I did not foresee the future. But [the recognition] feels really good. That's a nice pat on the back."

Most of the brand's marketing is done through social media - where the brunette beauty announces product launches, previews new items and tells fans which shades she's wearing each day - to her 175 million-plus fan base across Instagram, Facebook and Twitter and Kylie believes it's been essential to her success.

She added: "It's the power of social media. I had such a strong reach before I was able to start anything."

Kylie has overtaken Facebook founder Mark Zuckerberg, who previously held the title of youngest self-made billionaire from the age of 23.

The make-up mogul signed an exclusive distribution deal in November last year with beauty store chain Ulta to stock her $29 lip kits - a matte liquid lipstick and matching lip liner - into the company's 1,000-plus stores across 50 states in the US, having previously sold only online or occasionally at pop-up shops.

Following her deal with the beauty company, Kylie Cosmetics sold $54.5 million worth of products in just six weeks, according to estimates from Oppenheimer.

Kylie owns her entire company, which she started in 2015, and has just seven full-time and five part-time employees, while manufacturing and packaging is outsourced to Seed Beauty and her mother Kris Jenner helps run the brand's finances and PR.