How is it possible for an item to have 300+ stat?

I just saw an amulet on the Auction House with 325 Dexterity. I was under the impression that the max was 200, so I went into the DiabloNut affix page and looked for the Dex ones.

Apparently you can have only 100 Dexterity from the +Dex affix, but you can have up to 300 from DexVit, DexInt, etc.

Does this mean that the maximum possible on an item is 400? For one stat that is, I am sure you can't have 400 for multiple stats.