> But there's no huge corporate health insurance tax, and she won't be spending as much on commuting.

... and on housing. Even Europe's most nuts markets aka London, Berlin, Munich, Hamburg and Freakfurt don't come anywhere close to the situation in the US.

What's the situation in the US? You're obviously not talking about direct cost,

    Mean house price: 
       London: $753,793 USD
       USA: $369,147 USD

    Average rent per month:
       London: $2,992 USD
       USA: $1,699 USD

Or being cramped into small spaces,

    Average home size:
       London: 705 sq ft.
       USA: 1,800 sq ft.

Or homelessness,

    Estimated homeless population (% of total population):
       London: 2%
       USA: 0.2%

Perhaps you are referring to comments on HN?

    Annoying comments about housing posted on Hacker News:
       London: Not seen
       USA: Way too many

I think they meant comparable (i.e. desirable, world-class) cities in the US. You want to compare London to cities like Los Angeles, New York, etc.

That wouldn't be a US situation, then, only a New York, or Los Angeles, or wherever situation. But it clearly says it is a US situation.

Why do you get to cherry-pick London only then?

Because the original comment that was replied to cherry-picked London and compared it to the US. Start from the top.