Is it true that an eye is precious? And what about a kidney? We can survive without one of them, but in this way we are going to lose a part of ourselves and then, after such a changement, we have to take more care about us.
The Spanish use the expression “costar un ojo de la cara” or “costar un riñón” when something cost a lot to do (in money or effort terms).
For example: “Look at this car, I am sure it cost an arm and a leg”.