Its very difficult to compare QF's Europe ops to USA ops. The USA flight are all non-stop while the Europe flights involve an Asia stopover. So the Europe flights are a combination of through passengers and single-segment passengers. And on the shorter Asia-Aus segments they can carry significant amounts of freight to supplement the revenue from passenger fares.
The competition side of things on the Kangaroo route is skewed greatly by the lower labour and company operating costs of Asian and middle eastern carriers. They offer cheaper fares because they pay their staff peanuts (not just cabin crew, but all staff from janitors to execs) because their labour laws allow for very minimal conditions. Such staff treatment would not be permitted by an Australian or USA based airline. As a result, for QF to operate under Australian labour laws and to compete against airlines from countries with lower cost compliance, they have to operate on lower margins.
So a straight $/km airfare comparison may make sense from a passenger fare perspective, but is not reflective of the overall economics of operating the segment or an international airline.
As has been said so many times before, if the Pacific route is so lucrative, then why don't more USA-based airlines choose to fly the route, especially in these tough economic times? I think Delta joining the route is a great thing. They have a very good product and reputation and can bring innovation that UA has struggled to achieve.