Dave Gran at GoAheadTakeTheWheel has posted an interesting series of articles about the realities of professional road racing:

Introduction: Dark $ecrets The Realities of Professional Road Racing

This may or may not come as a surprise to you. Looks like Dave has done a lot of research for this series, and his numbers for the costs of rides at different levels are about in line with what I've known and expected.

The percentage of paid vs. paying drivers is interesting and not something easy to find out. If anything seem a bit optimistic, as Dave mentions. Salaries for actual paid drivers are interesting as well, and go up to higher then I expected!