Let's say I want to create a non-fungible token which represents a ticket to a venue. And I don't want ticket scalpers to buy tickets and resell these tickets for a higher price. It should only be possible to resell the ticket for the same or a lower price.
Does an ERC standard exist where one can set the maximum reselling price?
If not, how could this be achieved?
The best way I can think of right now is to copy the ERC721 contract and modify the transfer function. But then I lose all the benefits from ERC721 compatibility…
Best Answer
TL;DR
Adding an additional function in an ERC-1155 contract that handles the issuance of the ERC-721 tokens it contains. This function would have logic to check the amount of ether being sent to a method. If it's not enough,
mint
fails. If it's just enough,mint
goes through. If it's too much,mint
occurs and sends the extra back (minus tx fees) to the owner.Details
You will have to create an ERC-1155 collection responsible for minting the ERC-721 tokens and define custom logic for price. Any time
mint
,transfer
, ortransferTo
is called on the NFT, it must call the collection which owns it to determine if the price is enough, right, or too much.Use Cases
Your logic could be rigid, and place a hard cap on price, or dynamic to allow events like discounts to take place. Since your question is vague, I'll indulge both slightly.
A collection contains many ERC-721 NFTs which may have slightly different properties; a ticket would have metadata like
_section
,_seat
,_gameId
and_tokenId
.This is a novel area of development and ripe for improvisation and unique solutions. I would encourage you to think outside the box while working on this project.
Flexible
Unlike traditional markets, you don't need a counterparty to determine the price using this model. The price you get for an asset is determined by a formula. If I'm looking at a single source of ETH:DAI liquidity, and I want to buy all of the ETH, I could not, as each ETH purchased exponentially increases the price with zero as a limit, if either
x
ory
reach zero, the equation doesn't work, ourk
value goes to zero, making the asset unbuyable.Static Price
If you want a price set in stone with no change at all, collection need only to limit the maximum number of ETH that can be sent to call the
mint
function on an NFT within it, with remainder being returned to the purchasing account.But right now, prices are not always set in stone. There are early bird specials, discounts for purchasing many tickets (e.g. company gatherings), and even discounts after an underwhelming sale to fill seats are all commonplace.
You could loosely define the value of something (arbitrarily) as:
A ticket's has high utility, low/no ownership history impact, no future value, and liquidity varies (depending on number of sold out tickets, hype surrounding the event, number of seats). Compared to a piece of art that's sold 100 times which has low utility, high ownership history, potential future value, and liquidity without an ending time.
Since ownership history and future value are not important for tickets, we have liquidity (availability) and demand.
Where
demand
is dependent onavailability
. Your 1155 contract would set the initialdemand
value, and theavailability
is determined by the number of tokens not claimed by an address in the collection leading up to the event.A fixed price requires less code, as you simply need to set it's value in the purchasing token.
availability
is not part of any equation and serves only to see the remaining number of tickets.In the case of a fluctuating price,
demand
could be represented as a floating point variable between 0-1. When tickets first go on sale,demand
starts at 1 as zero tickets have been minted. We can approach zero, but can never reach it even if there is no demand for tickets as it creates a mathematical impossibility. It is likely thatdemand
will remain constant: people who want to go to something want to go to something regardless. If they can afford it, they'll go. The only thing this does is reduce the price proportionally depending on the number of requests for tickets, which is not unlike tickets to events today where promoters will give discounts just to fill the seats.Setting the equation up like this also prevents the price from going above the sale price as you cap
demand
at 1 in the controlling contract. However, you could alter this and allow for some resale within a reasonable range. If it's last minute, sometimes ticket prices do go up (scalpers or not). Perhaps settingdemand
to a floating point value slightly above one would make more sense.Note
If the NFT is controlled by an 1155 collection with custom logic, you can define any type of price issuance from fixed price to a bonding curve, or even lower the cost automatically if
N
number of tickets are still unsoldX
days prior to the event in order to sell out.