I was watching a show the other day about the Korean War and it stated that there were less than 100 miles of paved roads in the entire country in those days. Then take a look at Seoul's skyline today.
And a united Korea could be an even bigger economic powerhouse, but the leadership fears years of struggle integrating the North, so the situation perpetuates itself. And it makes integration appear more and more difficult as the gap between the free South and the enslaved North widens.