From the way I understand how this works, each trade of ETH creates a reportable gain or loss transaction
1) when you sold ETH and purchased the NFT, the price of ETH on that day, compared to when you first purchased ETH is a reportable gain or loss transaction
2) then when you sold the NFT, and purchased ETH, the NFT is a reportable gain or loss transactiion
3) when yiu eventually sell .5 ETH, there will be a reportable gain or loss transaction. The cost basis is the purchase price in 2) above.
