Why are international schools so expensive?

This is a question we get asked a lot:

Why do international schools in

Malaysia cost so much?

Most parents assume that international schools cost a lot because of their facilities: the swimming pools, the ICT labs, the fancy theatres and the music rooms. It's certainly true that these sorts of facilities are expensive to build and maintain. However, that's not the main reason international schools are expensive.

So what IS the answer? It's pretty simple.