I would probably say $30 - around $75 depending on where you get it. Make sure the bird is healthy before you buy it and has no worms. My brother got a yellow pearl cockatiel around Christmas time and it was $30.
Hopefully you find the bird you're looking for :)
Cockertiels can cost from a breeder 80 to 100....pet stores which are tyhe worst place to buy from can be from a hundred too 3 hundred.........buy from a breeder look up on craigs list in your area or on the web...good luck
I might be getting a cockatiel soon, and I really want one of the gray ones with a white face, like this one http://upload.wikimedia.org/wikipedia/commons/6/66/Cockatiel_Sleeping.jpg .
I know cockatiels costs vary based on mutation so how much would one like this cost?