Revisions log for Answer #1578

I would say it very much depends on the specific design. A beautifully filigreed one with glass glued in the corners and complicated load transfer in the lintel probably costs a lot more. With load-bearing wall beams and two pieces of window, it's not more expensive than two windows. I question whether you can still call it a corner window. There are many other variations in between (steel beams, wood beams for support, etc.). As you can see, it all depends on your aesthetic requirements and the skill of the planner.