This is truly a SUPER BUG, and it was only fixed in WoG. When you are in the artifact market in the Tower, Dungeon, or Conflux, if you place a very expensive artifact in one of the five slots in your backpack and then highlight it with the cursor, the price appears (e.g., 12000). Then, if you move the backpack to the right or left (for example, along with the Vulnerability Orb, you put 20 scrolls in the backpack), you can sell other, cheaper artifacts (like scrolls) at the price of the relic. The bug works even in online games. It's terrible, but I don't know how to get rid of it – 3.2 doesn't fix this flaw, which is bad. But in WoG 3.58, everything is fine in this regard.