This article was written by a Suzuki parent who is also an economist. Her take is that makeup lessons make no economic sense; if ya miss, ya miss, and the teacher is under no obligation to provide makeups.
At the school where I do most of my teaching, the policy states that students get one makeup per semester for any lessons they miss. Teachers have to make up anything we miss, of course.
For my private students, I figure missed is missed...sometimes I have a contract with a similar policy, but more often, I don't get around to making it. I think the times I cancel and the times they cancel tend to even out, and I don't make up the ones I cancel. I have a good rapport with all my private families at the moment.
I should still probably have a contract though.