Tree Magic, Purple Chia (Book/Helmet/Amulet/etc), Doglefox Colouring Book, and Cloud Shoyru (Apple/Ball/etc) are all code items, so there aren't many of them
but they don't have many people vying after them either, so the price for the seller and the price for the buyer might be tens of million NP apart. The most common items are going to be the Cloud Shoyru set.
Rod of Ummagine is several million NP, but it suffers the same problem code items will, as do all 'collectibles'.
Flaming Evil Coconut will (at least, has in the past) garner more interest because it's an LC item, but I think you will still have a hard time finding a buyer. The current seller is asking for WotDF, which seems like a lot to me.
Ace is asking 250m, but I'd wager a fair bit less than that
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