There are a few things that could be improved for Cardano NFT sales:
Currently, when you put an NFT up for sale on an NFT marketplace it says it is “sent”. Later, when that NFT is sold it does not say it is a “trade” but instead simply says a “receive” tx of the income from the sale. It would be nice to have better handling of these trades so they are identified as “trades” and the values are calculated.