It's pretty weird that Kodak doesn't just make them available as a normal product any more. You'd think students would want 100' rolls on a camera spool to save money while learning to shoot, for instance. They still made color negative motion picture film available that way even recently... though now that I look at their catalog it looks like that is gone too. So maybe this is the cost involved when they no longer have a warehouse full of the camera spools and 100' bags and cans around?!
Orwo will gladly sell you two different kinds of B&W movie film in 35mmx100' for less than half of what Kodak is asking:
Or if you really want Double-X, this should would provide some incentive to get equipped to deal with the longer rolls! It's only $150 for 400' brand new ordered direct from Kodak.