I remember a NOVA on one of the Mars landers. Nobody had ever landed anything on Mars with a parachute before, so the developers had a massive problem. They built this humongous facility to test parachutes. One design after another failed, for several months. They finally found a design that worked.

I don't know what building a second chute would cost, but I bet it would be less than one thousandth of the cost of #1.