Yet more of those big old houses

Below are a few more of the beautiful homes that appear all over the place in Kew Gardens. Now that Buddy and I are walking around the neighborhood regularly, I'm admiring these houses more and more. Why can't the builders of today's cookie-cutter mc'mansions make houses as nicely as these. Are they really that much more costly to build? I have a feeling that well-to-do buyers would pay the difference in return for a well made home. They are all 80 to 100 years old.