The seat belts are designed that way to allow car seats to be secured back there for children. Could they be longer? Sure. Would I consider it a defect in the JK design? No.
I've got an '08 as well, and none of my passengers have complained. That doesn't make your problem any less real, but I hope it sheds some light.
As far as dealers go, giving out those extensions for free as a matter of policy would be a decision the owner would have to make. I'm certain that the dealer does have to pay something for the seatbelt extension...but I'm pretty sure it's not $55. I'd wager that the only way that you can push the dealer into giving you free extensions is to show them a recall notice or TSB indicating that Chrysler has recognized this as an issue with the JK. As far as charging you to check something out and say "it's fine"...that seems par for the course for dealers in Calgary. That's part of why so many of us help each other diagnosing our jeep issues.