I understand (I think) how to assign cost basis (for income tax) to ordinary minted NFTs: Convert the minting price (including gas, fees, etc.) in cryptocurrency to dollars using the market rate at the time.
But when a single transaction yields multiple NFTs, how do you divide the cost basis among them?
For example, here's an Ethereum Ethereum transaction in which the originator sent 2.474 Ether (including gas) and received two Raid Party Fighter tokens and one Raid Party Hero token. The Fighter and Hero tokens had different collection sizes and radically different floor prices at the time.
Suppose the minter kept one of the tokens and sold the other two. How would we assign the total cost basis for the transaction to the three individual tokens? Do we just divide the total cost by three? Or do we try to account for the relative estimated values of the individual items?
Is there a hard and fast rule for this, or is there room for discretion?
I assume there's some non-crypto analog for this situation, for example (maybe) buying multiple non-fungible items in a single lot at auction. I would appreciate any insight whether cryptocurrency-specific or not.