PRIVATE school: $32,000 a year per student. Mortgage: $96,000 a year. Co-op maintenance fee: $96,000 a year. Nanny: $45,000 a year. We are already at $269,000, and we haven’t even gotten to taxes yet. Five hundred thousand dollars — the amount President Obama wants to set as the top pay for banking executives whose firms accept government bailout money — seems like a lot, and it is a lot. To many people in many places, it is a princely sum to live on. But in the neighborhoods of New York City and its suburban enclaves where successful bankers live, half...