When you consider the differing regulation and applications, it makes a great deal of sense. Just making a window in the US can cost less than $10 if you hand assemble it. Making a window that conforms to all building regulations in your particular area is a huge undertaking that involves highly specialized equipment.

I'd never thought of it that way, but you're absolutely right, particularly in Germany, by a factor of at least 3-4. 50-55" mid-range TV: plenty under 400 EUR. Double-glazed window about that size, custom-made (because just about all windows in Germany are custom-made): 1200 EUR, and that was about six years ago - I shudder to think what it would be now.