Some people (1% of the WoW community?) might not know about this, some of the cata BoE's can be equipped at level 77.
Some people are lazy (99% of the WoW community?), so what do they do with the green BoE's that they will get from leveling in Hyjal/Vashj'ir/Uldum? Well, they probably want to get rid of it fast, fast, fast! They post it on the AH for a small amount of gold.
Some people are clever (like me), so they buy the cata BoE's up that is going for 15-40g and resell them for a bigger amount of gold.
So you see that I'm tired and when I'm tired I like to write stuff, useless stuff.
So to summ it all up:
1. Go to the auction house.
2. Search for cloth/leather/mail/plate gear, all of them! In the level range of 77-79.
3. Check so they are atleast ilvl 272 or higher (it's a cata item then, duh!).
4. Buy the cheap ones, those at 0g-60g.
5. Resell them for a higher amount 100g-150g, yeah, you name it!
So obviously, this also works for weapons, same method but with the weapons tab at the auction house!