The answer is in the name of the token : SuperRare.
There is a negative correlation between the value of an asset and its total supply, even when the tokens are non fongible.
That's why we see some NFTs being sold for 100 ETH.
Holders can be both creators and collectors :
- creators when the NFT is minted, it can then be put in auction for exemple
- collectors when the NFT is traded.
For the submit token burn details info I believe this is an option for the contract owner who can communicate to Etherscan the token’s burn history.
UPDATE
The SuperRare smart contract implements ERC721Enumerable. In this contract we have the array _allTokens counting the number of NFTs :
// Array with all token ids, used for enumeration
uint256[] private _allTokens;
Then we have the totalSupply function which returns the length of the previous array :
/**
* @dev Gets the total amount of tokens stored by the contract
* @return uint256 representing the total amount of tokens
*/
function totalSupply() public view returns (uint256) {
return _allTokens.length;
}
Note that (unlike ERC20), the totalSupply method is not part of the base ERC721 standard, but is implemented by ERC721Enumerable which is an enumeration extension smart contract for ERC721.
Finally the mint function :
/**
* @dev Internal function to mint a new token
* Reverts if the given token ID already exists
* @param to address the beneficiary that will own the minted token
* @param tokenId uint256 ID of the token to be minted by the
msg.sender
*/
function _mint(address to, uint256 tokenId) internal {
super._mint(to, tokenId);
_allTokensIndex[tokenId] = _allTokens.length;
_allTokens.push(tokenId);
}
We can see the _allTokens array is incremented after a mint. Conversely, it is decremented after a burn.
The totalSupply is therefore not fixed, which is logical given the ambition of the project to create an art marketplace.
It appears you are very early in the design process and are still studying existing solutions. So I'll reply here with just some broad concepts. Good luck on your journey!
Fully off-chain
This is the approach OpenSea uses. Everybody with a token needs to approve or, more likely, approveForAll their tokens to the OpenSea marketplace contract.
Commitments are created by signing "messages". These are off-chain transactions. However, cancelling transactions requires posting on-chain.
The main criticism of this approach is that it is centralized--third parties cannot read the order book in a first-party way.
But the benefit is strong, this is almost the cheapest way to implement a marketplace.*
*A slightly cheaper way involves batching the "cancel" transactions and is technically an L-2 solution.
Fully on-chain
Here the order book is entirely on-chain for inspection and action. The market continues to work even if the Web2 website is offline.
I have studied CryptoPunks and most recently released the Area market contract that implements this. Please see: https://github.com/AreaWorld/ethereum-contracts
This is fully transparent and works entirely without a website.
There are more partially-on-chain solutions that mix the benefits of economy and decentralization. Building a marketplace requires careful implementation. I recently did a review of Number Board and found problems, you can see this publication for some hints https://privacylog.blogspot.com/2021/09/implementation-issues-make-number-board.html
Best Answer
As Ismael points to in the comments, it would seem that the author of the linked comment in the OP's question was not pointing to SuperRare being on-chain and Foundation off-chain, but was emphasizing that the value of SuperRare as a curator. The "on-chain" provenance comment likely means that being able to point to an NFTs on-chain history means it can be traced back to where it was purchased from on-chain, and having been in SuperRare is part of what one is purchasing when they purchase such an NFT (in the thread author's opinion.)
There's something we should really unpack here as an additional note on the question: NFTs, according to the ERC-721 (and 1155) standard that they are based on, do not (generally) "include" a JPEG or other image. There is generally a field in the NFT that contains some kind of pointer (if you look at the standard, this is the extension called the Metadata extension) traditionally a URL or IPFS (or similar) hash, to a JSON. The JSON, in turn, links to the media. This is very significant, as it means in many cases that the media can become either unlinked (in the case of the JSON pointing to a centralized IPFS gateway, for example) or even actively changed (in the case of it pointing to someone's traditional web site, for example). That's a bit tangential, but very useful in terms of understanding NFTs.