Besides the usual 2.5% commission, NFTs minted on OpenSea are known to be free to list with a price since OpenSea does not take custody of the NFT anytime during the sale process. Does it though as soon as an offer or sale is accepted on an NFT that was listed there?
Why does OpenSea run gas free for sellers, whereas alot of curated NFT platforms charge gas fees?
Best Answer
https://opensea.io/blog/announcements/introducing-the-collection-manager/
Anytime a write happens to the blockchain gas fees have to be paid.
There is nothing special about OpenSea's smart contract that allows them to avoid paying gas fees up front when creating the NFT.
OpenSeas creates an NFT, but defers writing to the blockchain until time of purchase. At that time gas fees imposed on the buyer to assign ownership of the NFT. The approach encourages sellers to list more items because they will not need to pay any fees up front.
Some users may object to this because if an NFT isn't written to the blockchain, then they do not consider it a real NFT because the non-fungible aspect derives from being written to the blockchain.