As I read more, I'm pretty sure the child in question was 15. It doesn't necessarily make it ok but it does seem like this article's title is pretty inaccurate. The conversation where the term "whale" was used was referring to a 15 year old that had spent around $6500.
The problem is not the relative amount of money being spent by a family's child whether that family be wealthy or of means.
The problem is that five-year-old children cannot provide informed consent.
EDIT: remove superfluous "the".