Most Expensive Material

[Stallion]

So... what is the most expensive material in the game (other than Riverine, if it is)?

[Hirax]

Not really a material, but Susalian Chainweave is +28,000 GP for light armor, +35,000 for Medium, +42,000 for heavy. Thinaun is +10,000 for a light weapon, +15,000 for a 1 hand weapon, and +20,000 for a 2 hander. Both are from COmplete Warrior.

[The Rabbler]

Riverine costs something like 1,000gp for each pound it weighs.

[JaronK]

Oearthblood is pretty expensive, as is Obdurium.

JaronK

[Cog]

Riverine costs something like 1,000gp for each pound it weighs.
Double that, actually. Sizing might be a very good investment.

[Sacrieur]

Blended Quartz (A&EG page 18) costs 2000 gp/lb.

[Thurbane]

Not including gemstones, I assume? Cause diamond is bound to be worth a lot by the pound...

[Darrin]

So... what is the most expensive material in the game (other than Riverine, if it is)?

Assuming one dose of poison is an ounce, Pit Fiend Venom (Dungeonscape p. 129) is 30,000 GP per ounce.

[Greymane]

Assuming one dose of poison is an ounce, Pit Fiend Venom (Dungeonscape p. 129) is 30,000 GP per ounce.

Now I'm imagining a crew of redneck-sounding yugoloths chasing down pit fiends (on mounts with magic ropes) and hogtying them.

Then harvest the poison and take a few trophy photos. Then leaving the confused pit fiend there.

[Anxe]

Look at your character's armor, now back to me, The ARMOR IS NOW DIAMONDS!

There are some third party materials more expensive than those listed, but who cares about those? Also, in one of the old Dragon or Dungeon issues about Drow there was a type of armor material (Spiderslik) that had no check penalty or max dex bonus. That'd be my guess for most expensive, and it is made by Wizards. You'd have to find which magazine its from on your own though. Sorry.