Cousins NFT marketplace is Stargaze. Besides buying and selling Cousins NFT in this NFT marketplace you can also trade plenty of other NFT projects from Stargaze.
As with any IBC network (built on Cosmos-SDK), the transaction fees are minimal, making the marketplace superior to many other non-IBC marketplaces and non-IBC networks (e.g. Ethereum). What’s more, is that transactions in Stargaze are lightning-fast compared to other non-IBC marketplaces and non-IBC networks (e.g. Ethereum and Solana).
The main purpose of Stargaze is for you to buy and sell NFTs with ease, at minimal transaction fees. The royalties vary between NFT projects with information disclosed on the specific marketplace page for Cousins NFT.