UA has drastically cut capacity in NYC since 2000, reducing the 767 JFK transcons to 757 p.s. and gutting EWR. Of the choices mentioned, p.s. to LAX or SFO has greatly reduced capacity, with UA handing the low end to B6. LGA-SNA is going to command a price since it is between the two of the most restricted airports in the country.

There are no low prices becuase UA figures that by the time of the flight, they will have sold most of the seats, even at the higher price. AA, DL, CO and B6 dominate New York and for the most part, UA is letting them have it, maintaining only enough capacity for business travelers. By the time most business travelers would book NYC-SNA, most flights would be around $600. That is still cheap by 1990s standards, when such a flight would often cost $2,400. You did get a free hot meal and were more likely to arrive on time however.