Sounds about right. The problem with the raw capitalism model in the modern world is simply dependence on other systems. People can be exploited when they NEED products like food, water, and energy. Permacultre provides mechanisms to alleviate these needs, which creates a surplus of abundance (read that in Lawton's voice), and consequently lowers demand for the product. Lower demand = lower prices.
Is it possible (in theory) for every individual in the world to be a self sufficient "island"? What about every family? Every neighborhood? Wherever you draw the line, these autonomous islands can now participate in voluntary interaction with the other islands.
When analyzing the ethics of a economic system we have to consider individual rights as well. The existence of a right like freedom of speech doesn't immediately place a burden on other people. Healthcare and education are the products of another person's labor. And the right to another person's labor is slavery. This of course brings in all sorts of moral issues with taxation and collectivism. Can permaculture design provide ample healthcare and education for the world's population? If not, how much can it reduce the need for these products?
There's so much to consider when designing an economic system with permaculture as a fundamental principal. Balancing the potential of abuse and individual freedom is difficult and messy. Perhaps we need another ethic that simply states "Don't be an asshole."
But whether you're a communist, capitalist, or anything in between, driving self reliance (via permaculture) as close to the individual level as possible should be a priority.