$18,000 to learn bronze?

I've just done bronze & silver international ballroom on the back of six months of private lessons at £12/week, so that's just over £300. I passed with HC, so the teacher wasn't cutting corners (and, for example, my Waltz routine included 15 figures, when the syllabus required a minimum of just 6).

Are the US dance studios run by the mob? Do privately owned schools just "disappear"? Why do you pay such silly money?