A 26-year-old Singaporean geek turned down US$100m for his app. It was a great call

A few years ago, Quek Siu Rui huddled with the board of his Singapore start-up to consider whether to sell. Quek was only 26 and the US$100 million offer would have made him wealthy beyond his dreams. But he said no: He wanted to keep building the business.

Excellent call. Quek’s company, an app for selling used goods called Carousell, is now valued at about $500 million, according to a person familiar with the matter. The CEO doesn’t regret his choice. “This is a once-in-a-lifetime opportunity,’’ Quek said in an interview. “We want to build an enduring company.”

Six-year-old Carousell operates in seven markets including Singapore, Hong Kong and Australia and is one of the region’s most popular virtual flea markets. People use it to sell everything from second-hand cars and couches to game consoles and, as of this week, purple wigs.

After raising US$85 million in a recent funding round, Carousell plans to build out its existing markets, which also include Indonesia, the Philippines and Taiwan, before expanding to more countries. It’s part of a league of classified marketplaces, including Seattle-based OfferUp Inc and Japan’s Mercari Inc that are aiming to challenge eBay and Craigslist.

“Carousell started in a fresh market with a new product offering that was tailored for Southeast Asia,’’ said Vinnie Lauria, founding partner at Singapore-based Golden Gate Ventures, a long-time Carousell backer.

Quek and his partners, Lucas Ngoo and Marcus Tan, got to know each other as students at the National University of Singapore. The self-described geeks bonded over their hobby of buying and selling gadgets online. As part of a university programme, they spent a year in Silicon Valley and attended talks by entrepreneurs, including Facebook Inc. founder Mark Zuckerberg.