There's a article in the June 2004 issue of Airline Business titled "US Airways Reinvented". Not much written in the article that many here don't already know, but there is included an interesting paragraph comparing US Airways' operating costs of a 737-300 against a unidentified LCC who operates 737s.
Third Paragraph:
"The carrier (meaning US Airways) is clear that it must still lower costs. Its trip cost between Phildelphia and Orlando is over $14,000 with a 126-seat Boeing 737-300, while an unidentified low-cost carrier's is under $8,000 with a one-class 137-seat 737-300. So the US Airways break-even fare at an 83% load factor is $135, while that of the low cost carrier's is $70 at the same load factor."
Third Paragraph:
"The carrier (meaning US Airways) is clear that it must still lower costs. Its trip cost between Phildelphia and Orlando is over $14,000 with a 126-seat Boeing 737-300, while an unidentified low-cost carrier's is under $8,000 with a one-class 137-seat 737-300. So the US Airways break-even fare at an 83% load factor is $135, while that of the low cost carrier's is $70 at the same load factor."