Often you can find people selling things for to high a price, or see a dispute about how much something's really worth. Here I'll show the average prices for most items. [Note: These are all from personal experience and change often. I will edit the thread if needed]


Rare-ish items (Donor kits, donator kits)

Iron: Around $500 or so, is sold in the admin shop for a slightly higher price.
Redstone: $25 a piece
Grass: Around $550
Diamonds: $6000-$8000
Spawners: $11,000-15,000

Rare Items

Mob heads: $100,000 and up. Depending on what head
Spawn eggs: $50,000-$100,00+ depending on what mob
Beacons: Around $100,000-$150,000
Fire/lava/water blocks: Previously over $500,000 Currently unset price due to the 1.8 update.

Regular Blocks

Wood (Logs): $80-$120 per stack
Cobblestone: $20 per stack
Stone & Stone Brick: $30-50 per stack
Wool: $100-$300 per stack (depending on color)

[May add in other items in the future. I did this while doing homework.]

 

You forgot gravel, ice, sand, dirt, glass , edit them in skrub

 

Bish dem illegals, me dun wanna get bunned skrub

 

Might wanna edit in things that will never change in value: gravel, dirt, glass, they're all worth $0, and they're staying that way

 

Right, their value will always be zero, because they are illegal to trade. This is a price list, not an illegal items list.