I haven't sold any, but I wouldn't let mine go for a penny less than $25 a piece. Maybe $20, but that would not even be primed or anything.
I even have aluminum covers on the lids (just flashing).
Your time is worth something. My wife keeps telling me that if I don't place a fair value on what it is I do, no one else will.
If folks don't want to pay that, let them go pick up a sheet of plywood, haul it home, cut it up, glue it and nail it together.