International Business Corporations are ridiculously common. You don't have to be rich, many people with average income have those.
I would be surprised if that's true. How common are IBCs among people making, say, $50k (the median U.S. household income)? How about even $80k, or $120k? My guess is that they're negligible until you get to more like $500k+, though I'd be interested in some numbers either way.