Basically, items can get a stat that is "Reduces required level by X" where the reduction can go as high as 12. This means that you can have a 300+ dps weapon that should be level 55-60 useable in the 40's... which makes you a god.
The thing is, when you are a level 45 character on the auction house and search using the "smart search" function for a weapon, you won't see a weapon that is level 55 but only requires level 45 due to this stat.
As far as the AH is concerned, it won't show you that item until your character reaches the level to use it if it didn't have its level requirement reduced. If you want to find these items, just search for items in the level range a few levels above your character and filter by the reduced level requirement stat.
So, since a lot of people use smart search and havent seen these items yet, they're still really cheap. You can get weapons with over 100 dps more than the other weapons of that level for cheaper.
This works best around level 48-53 items that are actually 57-60 requirement because the dps ramps up SO fast between 50-60.
