EDIT --Per SKS at the SHM, Wave gets between "just above a dollar" to "just under ten dollars" per drive based on what is bundled, who the oem is, etc. There are many levels, so there is no one set pricing structure for the drive. It is based on product, volume and OEM specific developments.
EDIT, with Dell, it has been "hinted" that since they requested the most customization to the software and interface, they would be paying the most, at the top of the range, figuring a conservative $7.