You can also always trade for the higher value / popular items. Of course you don't have to have higher value / popular items to sell, it's just easier since you can understand how the buyer doesn't want to risk their account buying things they can get easily get on the Neopets site legitly.

You can sell them like what bianca suggested gifting it to a shell then either gift it again or give that shell account to the buyer. Either way you do have to get gift boxes... Also leaving the items on the shell account (using a different IP) for a couple weeks before actually selling it will helps a bit.