A sixth-grader was very happy to find a used copy of the beginner method I use for lessons at Half Price Books for literally half price. And she was very surprised--as was I--that said book had my handwriting in it...as well as my beginner outline, my attendance policy contract, and some random flute music.
(Considering that the attendance contract has my name, address
and phone number on it, I'm glad that it was sold to my student and not
a stranger, though I guess I could have potentially picked up a new
student in the latter case.)
UPDATE: Just a clarification: The
book in question has my handwriting in it because I taught a previous
student out of it, rather than it being my own former personal book. I
don't think I've ever sold back a music book; even my old Grout music
history text is still on the shelf (though I did ceremoniously burn the
paper cover when I finished that sequence of classes).