While a taxi to SGS should be 400 baht maximum (usually closer to 300) and the taxi's are in relatively good condition, larrylim would almost definitely have needed 2 taxis for him, his wife, his baby, his parents and the luggage.

In general, using the various taxi services at the BKK airport is never a good economic choice. However, things that are too expensive in Thailand tend to be not so much money. In this case, paying $12-$15 extra to share the car and not split up the family is a decision that many people would make. Also, the airport is a bit chaotic with many people offering you a taxi ride and no one letting you know exactly where to go to get the official taxis.

I think as a traveler to Thailand, people should know that the taxi situation in BKK is pretty reliable and economical. People's antennae for being ripped off need to be raised while in Thailand, but if you get to the right taxi line that fear can be delayed until the next encounter with a Thai person who takes an interest in helping you.