seat cost per mile isn't the only factor any more.
A) engines currently are fairly conservative on that thing; they designed it for later versions to "Fit in" more powerful engines. That in turn will allow them to use more of that deck space. Read 800 pax cattle cars.
B) 4 engines and running that close to the limits means that it will be slow to climb; that's gonna mean tacking an extra half-hour or more on long haul flights, which does have an economic impact on operational costs. I'll eat my hat if that thing climbs fully loaded faster than the curvature of the earth.
C) Large capacity may mean fitting more people in a landing slot at crowded airports, and that's supposed to be the market (hence not just seat cost, but how many seats). But do a mental note of the flights you've made in the past five years -- how many of them would be "A-380 Territory"?
D) An already complicated system has further strains added by political concerns that decentralize every aspect of the aircraft's design, construction and assembly. Even worse, there are politicians who see this project as a European Statement. You'd hope that Europeans, as backwards as they are, could take a couple lessons from the past: the soviet missile program, the Concorde and Tupolev, that whole "Schoolteacher in Space" thing. Let business determine what's good business.
E) Load factors. What kind of load factor does that thing need to break even?
So basically, we get the A-380, a whale of an aircraft marginally bigger than a 747-400 (which can cram up to 568 pax, by the way, but not conceivably on long hauls), but with considerably worse performance, as-yet undetermined operating costs, and some interesting problems with passenger handling: even if they upgrade the physical aspects of the airports in time, there's still the baggage handling and boarding time/space. When the A-380 comes out with the 800-passenger version, is it going to be popular with ground crews and passengers? do you mind boarding your 14-hour flight 1.5 hours early, then waiting another hour at the other end for your bags?
It could do very well, but Boeing's only sold something like 1400 747s in 35 years. To "Break Even" at 325 aircraft, the A380 would have to match Boeing's figures for 8 years.
So even the orders they've got are probably skittish. If boarding/deplaning is a nightmare, or if -- heaven forfend -- something should happen (like Swissair's MD-11), the A-380 could run a quick and nasty death.
Of course, it could do really well too. The folks in Toulouse know they've only got one shot at this.
