Does your friend give them actual, meaningful raises as they grow? Is he actually paying competitively to begin with?
Because I think if you have this pattern that consistently, it's really likely that either you're underpaying to begin with or your raises suck or are not even present.
I love working at small companies. It's by far my preference. But none of the small companies I've ever worked at offered anything like the comp and comp growth that the big corp I currently work at does. In fact, almost all of them offered me near zero compensation growth over time. And in real dollars that effectively means negative growth.