Except that DL, UA, AA, US have costs that WN doesn't have and mainline to mainline doesn't reflect the total cost of operation for the network carriers. I can say I'm saving every dime I take in (disregarding all spending). While it's a true statement, it gives a distorted picture. It costs US, UA, AA, DL $X to operate their system and the system produces Y ASM's. So $X/Y = CASM. Now I could say that the US 330's cost $X to operate/year and they produce Y ASM's per year so $X/Y = US' CASM*** and be absolutely correct as long as somewhere those *** say that it's for the A330 operation only, but it doesn't really mean anything. I prefer giving an accurate picture rather than making any specific carrier look better than another.
Jim