In case anyone is wandering in here who doesn't know the Bluebook, it's essentially a style manual for law review article citations. Courts generally have their own style for citation of common sources, such as cases, statutes, and law review articles, but may require Bluebook style for unusual sources. As a lawyer who drafts appellate court dispositions, I consult it once or twice a year, and basically never see a citation from a party that would require it.
The people who do need to consult the Bluebook regularly are law students and law professors. This could be a big deal for them. However, this is more of a "tyrany of the textbook publishers" issue than a "paying for the law issue."
By the way, if anyone needs to know how to do citations for Illinois courts, I offer you this (pdf): it's the courts' internal style manual, so it has information that a party won't need, but it will tell you how to cite authority. It will also send you to the Bluebook occasionally. However, the actual rules for brief don't require you to follow that format; anything clear and consistent will be fine.