What cheap taxis? I don't consider taxis in Korea to be cheap anymore. 10 or 15 years ago, yes, but not these days. Certainly cheaper than some places but very expensive when compared to a lot of South East Asia for example. Maybe I'm missing out though on a cheaper alternative to the standard metered taxis?

A fourth reason why the train is really useless is the price. Even with all it's disadvantages, the express train is still priced much more than a more comfortable and convenient luxury limousine bus.