Rocket Raccoon loves collecting people's body parts. No one knows why, except maybe he knows how valuable these parts are to their owners. After all, who would want to wake up missing an eye or an arm?
Our limbs (肢体) are so precious that the value of them should be very high.
Indeed, when something costs a lot of money, we tend to say it costs an arm and a leg. International university student tuition? That's definitely going to cost an arm and a leg.