Hours before closing the $44 billion acquisition of Twitter Inc, Elon Musk said he bought the social media platform to help humanity, not to make more money.

According to the Bloomberg Billionaires Index calculations, the world’s richest man, who now calls himself “Chief Twit,” lost an immediate net worth of $10 billion by finalising the deal.

Musk, 51, has spent at least $25 billion starting in April to fulfil his agreement to buy Twitter for $54.20 a share, provided he retains outside investors who pledged $7.1 billion for the deal.

But six months after Musk announced he would buy the company; his offer looked very expensive. Shares of social media companies tumbled as economic uncertainty, and rising interest rates dampened speculation and advertiser spending.

The Solactive Social Media Index, which tracks the performance of publicly traded social media companies, fell nearly 40%. The Bloomberg Wealth Index also factored in a similar drop in Twitter’s value, which affected Musk’s stake.

Other peers fared worse. Shares of Meta Platforms Inc, owner of the Facebook and Instagram networks, have fallen 53% since Musk made an offer to Twitter in April, wiping CEO Mark Zuckerberg’s fortune by more than $100 billion from its peak. Snap Inc fell 70% during the period, erasing the wealth of its co-founders.

Musk isn’t the only Twitter investor to take a hit. Company co-founders Jack Dorsey and Prince Alwaleed Bin Talal al Saud backed the acquisition and are believed to remain investors in the company. Their wealth is estimated to have dropped by $380 million and $640 million, respectively.

For Twitter investors cashing out, Musk’s deal is a big win. When Musk made his offer to go private, he not only got a 20% premium but also avoided a downturn affecting rival social media giants.

It’s also a huge windfall for several outgoing Twitter executives, who will participate in nearly $100 million severance and payout. About half will go to former CEO Parag Agarwal.

Musk spent months trying to cancel Twitter’s bid. In July, he said he would end the deal because he was misled by bots popular on the web. Both sides took to the court after Twitter sued to force him to close the deal. Musk eventually agreed to go ahead with the original proposal.

Musk’s fortune took a $10 billion hit, bringing his total loss this year to $66 billion, according to the Bloomberg Wealth Index.

Shares of his most valuable asset, Tesla Inc, have fallen 35% this year, partly due to concerns that he would sell shares in the electric car maker to fund his purchases on Twitter. Musk used all of his available liquid assets to complete the acquisition of Twitter, increasing his estimated liabilities by $4.6 billion, according to Bloomberg indexes.