Here's another way to look at it.

Rather than simplistically calculating 360x your monthly payment and saying that's your "real" cost, you have to take into account how inflation eats away at the value of every dollar or Euro you'll pay a year from now, or two years, or ten... Then, you also need to subtract the monthly rent you'd pay if you didn't buy.

Here's how to look at things:

- Even if Marc put $0 down and borrowed the full $550k, his new monthly payment is $2626.

- Say he previously paid just $2000 in monthly rent, his cashflow burden increases by just $626.

- The rent will go up a little faster than inflation (an extra 1%/year in the US) while the mortgage payment will stay constant, assuming a 30-year fixed mortgage.

- If German inflation stays at its current 2.2%, in ten years Marc's rent would have increased to $2740 (at a 3.2% average annual rent increase), while his mortgage payment would still be $2626.

If Marc stays in the house long enough, the real cost of his mortgage payments would be less than the rent he would have paid over the same period. Plus, at the end, Marc can sell the house and net a profit.