In most cases, you can find a bird cage that would big enough and constructed well enough to properly house most parrot species for less than $500, but there are factors most people fail to realize when they do buy a bird cage:
Most bird cages under $500 won't last as long as your parrot lives.
By spending a little more on a cage made of aluminum or medical grade stainless steel, the cage will not corrode and will most likely last for the life of your bird.
You can also design your own bird cage and custom order it to fit your exact needs using aluminum where corrosion is possible, and other materials that enhance the beauty and longevity of your cage. It costs a little more, but you will end up with a "showpiece bird cage, that will last virtually forever.
If you are interested in calulating how much it will cost to design your own long lasting cage click here; Cages By Design.