David Vetter, known as "bubble boy," who died in 1984, is perhaps the most famous sufferer of severe combined immunodeficiency.
"He is dying to see a real rainbow," his mother said.
Gene therapies are probably still a decade away from being used routinely to treat genetic causes of hearing loss in humans.
The price likely won't be announced until January, according to a spokesperson.
But these breakthroughs are not going to come cheap.