DUB-SFO costs were more about low J class yield and high fuel costs than about airport charges. I'm not discounting charges but they were a lower factor.
Personally I think EI will wait for the A350 for DUB-SFO unless they get good 'new route' discounts from DAA and some form of guaranteed J class fares from the Irish/USA business community.
While I agree that Ireland-USA East routes are a lot less than 24 hours, thats if you do a quick turn on the other end. But EI don't always do quick turns,better to tweak the return time to suit pax requirements.
Eg. EI105 departs DUB at 1030, arrives back in at 0500 the next morning. So the guts of 20 hours due to the long turn on the ground at JFK.
And when being an armchair CEO and making up schedules/route maps, you have to take into account A332 vs A330 integration as well as planned maintenance downtime in between flights. Hence the cycling of aircraft through the route network. It is not as simple as "6 hours Eastbound plus 7 hours Westbound plus 2 hour turnaround= 15 per day for East coast flight".