Yeah I agree. I have a little definition of capitalism that I take a look at from time to time. It goes like this:

the process of saving, innovating and investing privately owned time and resources in such a way that it increases productivity and standard of living using the guidance of people’s subjective valuations. These subjective valuations are made visible through prices set through voluntary interactions on the free market.

This is my own definition, as I have understood it. It is not uncontroversial. And I am no expert.

Crusoe has a notion of prices, i.e subjective valuations, even though he is alone.

But for the sake of argument let’s say Friday shows up, and that Crusoe takes his net out two days a week and nets enough for both and gives Friday three of them a day and Friday returns X clay bricks a day. Q: What enables this exchange to take place? A: The initial investment of dried fish that converted into the net. That was the crucial part in my mind. The increase in capital if you will.

But yes I agree. A crucial part of the capitalistic system is the understanding that prices are discovered through demonstrated preference. Exchange.