Musk praised Bezos for investing his own money in Blue Origin

"Awesome," Musk commented below a video interview with Bezos on Fox News posted on Twitter this week. "Very happy that Jeff Bezos cares so much about the space field."

In the interview, the Amazon founder revealed that he "invested $28 billion of personal money" in Blue Origin since founding the space exploration company in 2000. Amazon's executive chairman, who currently owns assets worth about $300 billion, said it was time for him to stop investing his own capital because Blue Origin had just successfully raised more than $10 billion through its first external capital call.

"I now see Blue Origin's financial future relatively clearly. I don't want to receive capital from outside investors until I am sure this is a good investment for them," Bezos shared, and expects Blue Origin to become a public company through an IPO in the next few years.

According to Business Insider, Elon Musk and Jeff Bezos, the world's first and third richest people, are rivals in the private space industry. The two sides have had many fierce disputes over space launchers, government supply contracts, patents and personnel. Musk even quipped and nicknamed Bezos' company "Sue Origin".

However, the two billionaires still sometimes compliment each other. The SpaceX CEO once said he teased Bezos just to push his competitor to work harder at Blue Origin. His public praise of Bezos is considered by observers to be an acknowledgment of his opponent's spirit of dedication and huge resources devoted to the space industry.