I discovered a little bug in the new selling system (though it would have been a bug in the old system as well, had it happened then). I sold an XC-load of luxury goods, brought another, and got the exact same profit.

The first sale:


And the second:


Note that this is not just a bug in what is shown, I got the amount that it says both times (and several times before, when I hadn't yet realized that something screwy was happening).