It's come to our attention that Rare and Legendary items are common. These items which should be extremely valuable, are dropping off of mobs like crazy, causing the gold auction house to become flooded with these babies.
What's this mean to you? It simply means that if something drops a lot, you shouldn't expect to be able to sell them for much on the Auction Houses. When the item is coveted, but there are a ton on the AH, then we can expect the value to be very low. It's a basic supply and demand principle. If the items were hard to find and only 1-2 of them were on the AH, then we could expect the prices to be much higher. However this is not the case.
So, when you do come across Rare or Legendary items, make sure you either sell them for gold, or salvage them with a Nephalem Cube to sell the crafting materials/crafted items.
On the other hand, this is beta, and Blizzard could have increased the drop rate for beta (they never have before). In any case, keep your eyes on the AH and you will be able to tell what you should do, when the game goes live.