This isn't really true. I'd say the biggest cost seems to be the uncertainty of unification. That's why I believe South Koreans view unification with trepidation.
Germany saw vast inflows of foreign capital during this time that helped finance their unification.
Moreover, I would think that another twenty million consumers and cheap laborers and an entire half country to rebuild would be very profitable and much more useful than, let's say, speculating on whether land prices in Seoul will rise or not. Of course, then there's also the work that has been outsourced to countries like China can be brought back. There's actually studies that have shown that average South Korean incomes would continue to grow yearly (on average) after (peaceful) unification except that it just wouldn't grow as fast? That as a justification to "unification is too expensive" seems downright outrageous (In the meantime, the wealth gap between North and South grows unabated).
I think a lot of the trepidation in the South is that they would love to be reunified with their brethren in the North. However, remember that the reunification in Germany started when the EAST Germans started tearing down the wall.
I believe that the only way Korea will be reunited when the people in the NORTH refuse to deify the crazy Kim family and embrace their brethren in the South. The South understands they can’t use the tools of war to reunify successfully so they have to patiently wait until their brothers in the North rise up and throw off the commies just as the East Germans did.
As a justification, “unification is too expensive” seems downright outrageous? You just go ahead and be outraged, then, Joe. The Koreans I know seem to be right about there. Trust in government fits in, too. We probably would easily find many conservatives and small-business types who agree that our health insurance system needs some reform, but who don’t trust Obama, Pelosi, Reid, and the two Emanuels (professional slanderer, Chief of Staff Rahm and his brother, the plug-pulling “bioethicist” Ezekiel) to do the reforming. Likewise, almost any Korean with a business or a nest egg probably won’t trust the griftocrats in Seoul and the vicious, totalitarian Communist, serial liars up North to take on such a huge, risky operation.