The only criticism I would make of it is that it is not really comparing like with like.
You could buy a castle in Poland instead of an apartment in Chamwon-Dong but it would be very hard to commute to anywhere where you could earn a wage from it.
Seoul apt prices are not dissimilar to those of Madrid, Milan or Hamburg. To me it just shows that Korea has caught up with many European countries economically and now the squeeze is on for property.
Based on the same principal you could probably buy a small island of the coast of Jeollanam-do for the price of an upmarket Gangnam apt and build a castle yourself.