As you can see nowadays auction became close to funny, as some people 24/7 run from mailbox to auction npc for undercut. without giving a chance for normal players to sell anything. Some solution to this problem would be if you disable possibility to cancel auctions.
This has been done on any game with such feature, why would they prevent us to cancel our auctions? Would it be fun for you to put some valueable item 5k cheaper by mistake and being unable to cancel it ?
People who do that could get more of the item and just put new one to undercut. But you would not be able to cancel the auction you put. Doesn't seem like a good solution for you.