no idea about cost, but make sure you don't go off and buy a dog from somebody who breeds exclusively for "rare" colors. you're not going to do yourself or the pups any favors, just the breeder's bank account. familiarize yourself with the breed and the health concerns therein (they vary by size- but things to check for are hips and addisons disease in big dogs, knees in little dogs, PRA and sebaceous adenitis in all of them), and go from there. i understand color preference, but you're going to be hard pressed to find a responsibly bred phantom poodle.
which is silly, really, as it's a naturally occurring color in the breed, and it's just the whims of the AKC which make it "unacceptable".