Yes, exactly, the pitons could be made of iron rods, with leather for the foot pitons and wood for the hand pitons. That would mean that you would need eight iron for a full set. They would not be able to be diamond plated, because although diamond is nearly impossible to scratch, it shatters easily. Hand pitons would be able to be used as weapons, doing about 3-5 damage. For temporary routes, pitons would be well worth the materials, but watch out, because if your foot pitons wear out well you try to skirt a pit of lava, you will plummet to your death. You can stand attached to a wall even if you aren't holding hand pitons, so long as you are wearing foot pitons, but you can't travel anywhere with just foot pitons and no hand pitons.