Back in the good ol' days of the Internet bubble, the typical business model seemed to be to sell dollar bills for 99c apiece, and then make up the difference on volume. Things today are much more complex - now, the business model du jour is this - call a number in Iowa at standard call rates, then use the dialtone they give you to make free international calls to one of 50+ countries - for free. Did I mention that you get to do this for free?
How does it work? No idea.