Icy prism is a lootable JC-crafted item, which contains random blue gems worth 25-400 g.
Some people have posted about Icy Prism scams before but these don't work because:
1) You can have only one icy prism in your inventory and personal bank ("Unique Item")
2) You can't mail an icy prism ("Conjured Item")
3) You can't AH an icy prism ("Lootable item")
You'll likely find a willing buyer only if he can be in the same party, and see that you create the item.
Requirements: a Jewelcrafter who can craft Icy Prism, and access to a guild bank which can store multiple icy prisms.
Instructions:
1) Make an Icy Prism and loot any valuable gems (Dragon's Eye, Scarlet Ruby, Monarch Topaz).
2) Deposit the Icy Prism in a guild bank.
2) Advertise on the trade channel: "WTS Icy prism cooldown, 20 g"
3) Make a deal with the buyer and arrange a meeting in a bank
4) Craft the item after the buyer gives you the mats
5) Deposit the new Icy Prism in the guild bank and give your old icy prism to the buyer.
Profit = Probably around 150 g worth of gems + 20 g
Time spent = 2-10 min
Hints: Make sure that you have all the mats required to craft the item in the case that the buyer has trouble buying them on AH. Leave two cheap gems like Forest Emerald and Sky Sapphire in the icy prism, so the buyer won't become suspicious and report you. It's possible that an unopened icy prism actually contains only two cheap gems.