The man who founded IKEA, the world-famous Swedish furniture store, insists on flying economy and buying his clothes secondhand at flea markets.

One of the richest and most mysterious self-made billionaires, Ingvar Kamprad has an incredible rags to riches tale that began on the Elmtaryd family farm in the south of Sweden where he was born. Kamprad, who turns 90 this March, has an estimated net worth of $39.3 billion.

According to Business Insider, Kamprad began building his wealth at the age of 5 when he began selling matches. Five years later, the future billionaire grew his inventory and started selling Christmas cards, pencils and fish on his bike around the neighborhood.

Kamprad, who has dyslexia, founded IKEA in 1943 at the age of 17 after his father rewarded him with money for doing well in school. He started small by selling small items like picture frames before introducing furniture in 1948, which he delivered using milk trucks.

The name IKEA is derived from his first and last initials and the family farm he was born on near the village of Agunnaryd, in the Swedish province of Småland. IKEA would eventually become the innovator behind “flat packing.” By allowing shoppers to assemble their own furniture, IKEA was able to slash costs for consumers. Thus, the concept behind IKEA’s stylish, affordable, functional and ready-to-assemble products was born.

The Swedish furnishing retailer quickly became a global powerhouse. IKEA expanded throughout Sweden, Norway, Denmark and the rest of the world in 47 countries with more than 300 stores. As the popularity of IKEA grew, so did Kamprad’s fortune.

Despite becoming an ultra-wealthy businessman, Kamprad continues to live frugally. According to Daily Mail, he resides in an unassuming bungalow and prefers to eat the meatballs sold by his own store.

Though Kamprad has amassed a fortune, he maintains the image of a people’s man and remains conscientious of his money. He told a Swedish magazine the reason behind why he shops for secondhand clothes:

“It means that I want to set a good example. It’s in the nature of Småland to be thrifty.”

Kamprad’s frugalness is rooted in his humble beginnings. Though the furnishing industry magnate has enough money to buy a private jet, he insists on flying economy class. He even grocery shops at local markets at the end of the day in order to get better bargains. When Kamprad travels to visit new IKEA stores, he reportedly stays in cheap hotels. He has supposedly been driving the same old Volvo for two decades.

Kamprad was widowed after his wife passed in 2011. He is the father of an adopted daughter and three biological sons. His youngest son, Mathias, has had considerable influence on the growth of IKEA and was named chairman of Inter IKEA Holding SA in 2013.

Mathias controls Inter IKEA Group and oversees the operation of IKEA franchises around the world. Despite his age, Kamprad serves as senior advisor and the chief decision-maker of the revolutionary company he founded 73 years ago.