"People always conveniently forget as well that when you store data at S3 or Rackspace they're doing 3 replica's. If you store 3TB's, its not just the cost of a single 3TB drive..its 3x. To do it at home you'd need to buy 3x3TB Drives @300$ each."

Existing companies store multiple copies transparently...Either way, 1 copy or 3 copies, I dont think the math is wrong. Just change from 9$x to 3$x.