They fixed the overall bug that let you exploit the drop boxes in general. The exploit actually allowed you to sell as many of an item as the drop box had cash, regardless of how many of the item you had. Of course, you could also buy as much of an item as you had cash for,the Space Oddity painting just allowed you to really exploit the bug since it sold for a good amount but could be bought back for cheap. I made my money before they fixed the bug, fortunately, so by the time I finished the game I had more money than what I knew to do with. Equally fortunately, if future DLC allows you to contihue from the end game with the same V you finished with, I have plenty of those paintings in my stash in case I really need the money.