Why is us airways cheaper than united on same flight?

[Woodymd]

Why is it cheaper to book on Us Airways than United even though the flight is operated by United? Is there a difference in service or anything else? This is for a first class ticket from dulles to lax. Us Airways is 300 dollars cheaper and just trying to figure out why

Thanks

 

[PHL]

Their fare buckets aren't perfectly aligned. US probably charges one fare for any F ticket from IAD to LAX, which is trying to be competitive with UA on the same route that is nonstop (on UA metal vs. US metal). The codeshares fall into the same fare structure without any distinction for the fact that the flight is not on their own metal (US).

Book the US fare (on UA metal) and save the $300. There's no difference in service or anything else.