Aye, understandable it's frustrating to lose a sale to someone else. But if the other seller wasn't a 1 gil undercutter the result would have been exactly the same, except the market board history would show an item 20% cheaper was sold instead of yours. A 1 gil undercut actually gives you a better chance to get gil quick, since there's a chance to net the sale if you're on a different market area. But a 20% undercut is guaranteed to ruin your sale.
It's nice to imagine this, but it really doesn't.
Let's say an item is selling at 2m and has 7-8 sellers. 3-4 of those sellers might be happy making far less, but hey it's up at 2m so they'll list around that price. Then you come along and half the price to "send your message". It works on half the sellers, but a buyer doesn't come along fast enough and the other half go "oh well, a million is lots of gil!" and undercut you. The market for that item is now crashed to 1m and you haven't made your sale much faster.
I see this happen constantly.
