on ebay I found a few great cages for my cockatiels (I just dont have money to buy the cages) the cages I found are sturdy looking and bigger than you can find inside petsmart or petco like the one I would like to get is 32x20x53 inches plus it actually latches/locks close and is only $119
Now that you've gotten sources to find cages...I thought I'd give a couple brands that I have a preference for. King's Cages are my favorite, but they can be pretty pricy. My 2nd fav is Avian Adventures - they aren't as expensive and ver good cages.
There are a few things that I will spend more on depending on the brand name...cages, bird pellets, dog food, paper towels, etc.