Have you ever been in the bazaar, or just any vendor, in a hurry to sell your items and make some money? You're making money really quickly by going through and selling items you don't need!
Eventually you get to a certain section. For example, robes, and you sell a robe you really needed and worked so hard for. You don't notice that you sold it until you finish and check your backpack.
"Hey! Where'd my robe go?" You wander around and can't figure out where it went, and panic.
Suddenly... "Uh oh..." "I think I may have sold it on accident!" I have had many experiences in which this happened, and it is not fun. I think it would be good if there was a buyback system where you can look at things you bought recently, as in the past 24 hours. If you take back your descision, you could spent gold ( or crowns ) i don't really care which. But either way, you could get your item back and be exhausted.
"Phew.. I got my item back. That's a relief! Now I can go back to questing and not have to earn it again!"