I honestly haven't bent an aluminum arrow in the last year of shooting - hitting everything from rocks to trees to stumps. The only time I've bent a shaft, or mushroomed the arrow, is from a direct hit on a ceiling rafter back when I was shooting compound 7 years ago. (please don't ask).That same shot would destroy a carbon too, or at least make you think twice of using it again.
I'm not saying that carbon shafts aren't more durable - they obviously are. But I lose about a dozen arrows for every one I've destroyed, so any cost-benefit is lost to a guy like me.
Now, if you break more arrows than you lose, carbon begins to make sense. Not so with me.