Temporary costumes, hats, accessories, etc. (i.e. those available from Feso Shop) can be dumped into the Costume Collection Chest to exchange for a random cash shop item, such as Teleport Scroll, Soul Regen Potion, Boost Potion, Enchant Booster, etc.
So instead of letting those temporary costumes/accessories expire and vanish, you can trade them in for some random stuffs on the last day or even on the last hour. This should offset part of the cost of using temporary costumes/accessories. For example, a temporary hat costs 50k feso (i.e. about 2m vis in Orpesia). If you get a Enchant Booster (about 1.2m vis in Orpesia) from the chest, you have already been reimbursed more than 50% of the cost.
I got Soul Regen Potion... I suck.
Costume Collection Chests are situated near the Cash Shop NPC (Leticia) in Auch, Coimbra, and Reboldeaux.