Sales of nonfungible tokens (NFTs) have surged to record highs in the first half of 2021.

There has been $2.5 billion in NFT sales in the first six months of this year, according to DappRadar, a massive increase over the $13.7 million in sales for the same period in 2020.

Citing stats from Dune Analytics, Reuters reported that June has been a record month for the OpenSea NFT marketplace with almost $150 million in sales. This is almost one thousand percent higher than the sales figures for all markets over the entire first half of the previous year.

NFT buyers and enthusiasts view them as unique digital collectibles with intrinsic value because of their cultural significance. Others simply treat them as investments, speculating on rising prices.

According to NonFungible.com, which aggregates Ethereum-based NFT transactions, there have been between 10,000 and 20,000 buyers per week since early March. The NFT tracking and discovery platform reported that there had been $1.3 billion in sales for the period, but excluded around $8 billion in DeFi-based NFTs.

The most prolific NFT sale so far has been by renowned artist Beeple, with his “Everydays: The First 500 Days” fetching a staggering $69 million dollars in March following the Christie’s auction.

Sales figures from analytic platforms, such as DappRadar, only track on-chain transactions, meaning those sold at an auction may have had part of the transaction take place off-chain, so they must be manually added to the data, Reuters noted.

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Collectible and sports-themed NFTs are the most popular, according to data from NonFungible, with digital art coming in third place. Almost 300,000 sports-related tokens have been sold in the first half of the year compared to 124,000 for art. Its latest figure for June 6 reported just shy of 140,000 total NFT sales on the day for Ethereum-based tokens.

As reported by Cointelegraph in June, NFT transaction volume has multiplied by more than 25 since December 2020 as they usher in a new paradigm of interacting with culture, music, sports and the media.