For years we heard that ps was profitable (heck wasn't CLE holding it's own?), only to hear after the fact that UA was losing $$$ and they were moving to EWR. The funny thing is I saw a lot of the employee comments when they announced it internally and they weren't pretty...the natives are getting restless.
Notwithstanding the argument of EWR is no JFK, etc, UA should look at this as an example where if they really did lose money on prime routes like JFK-LAX/SFO its because they drove away their customers due to shortsighted changes or half-assed improvements/efforts. DL/AA/B6 all stepped up their game and UA took a tired sCO product slapped ps branding over it and assumed it was enough. There was no innovation, there was no product differentiation, it was just a cheap fix to say "oh look we have flatbeds on all flights" but nothing else. You still got the subpar post merger UA airport experience with irrops, SHARES metldowns, etc. So if UA lost money on JFK its not because there is no money to be made its because they basically took the wrong approach and didn't do anything extra to ensure they could make money.
The other thing I think about is the shortsighted CO approach of "EWR is NYC and people will fly us because we offer a better product." That might have been true 15 years ago because they did offer a product at or above what AA/UA were offering, but I don't know if its going to work this time around. Operationally I see the benefit of potentially feeding premium traffic from the west coast onward to Europe, but I'm inclined to believe with all the increasing LAX/SFO nonstops to Europe with connections over there that EWR really doesn't hold the same weight that it did in the past (in the sense that you really had to go to EWR/JFK to get to smaller European cities).