reason,
I am like you in that I will not go to Corona or anywhere in the IE for a cheaper home; however, many have, do and will. There is a critical price differential where people make that choice. For instance, imagine you could buy a large SFD in Corona for $1. Would you still chose to live in Irvine? Of course not. For me the cost differential would have to be so great that realistically, it would never happen, but there is some amount of cost savings that would drive me or anyone else out there. If that wasn't true, the whole IE would be empty right now. People didn't move out there because coastal living was bad: they moved out there for cheap housing.
People complain about the cost per square foot because it is a convenient comparative measure of cost. Houses are more expensive in Irvine, and they always will be. It is a matter of degree. If houses fall to $120 / SF in Corona, they will drop to $200 / SF in Irvine. Irvine will always command a premium for all the reasons we who live here understand, but this premium is not infinite, and if it becomes too large, people leave Irvine (or don't enter Irvine) for cheaper housing elsewhere.