The casualties will, and should, stun people. The Korean War, 1950-1953, total civilians killed/wounded: 2.5 million (wikipedia), and cost $341 billion in 2011 dollars (Congressional Research Service).
And then there will be a massive refugee problem on both sides.
So long as the planet of the population keeps going up and the population density of cities increases the chance of multiple millions of people being killed in a single military exchange keeps escalating.
I'd like to think we can keep a lid on things and work it out in a more civil manner, economically it makes more sense, but you know, dictators don't really care about economics as much as they do ego.
And then there will be a massive refugee problem on both sides.