I’m a socialist so no big fan of capitalism. That said, I don’t think capitalism is just about selling things for more than they’re worth.

We add value through our labor. Think of a log, it has some value as raw material. A worker might cut it into planks, and another might make a table out of it. It’s now worth more than when it started. The value came from our labor, and we should be compensated for it.

The issue with capitalism is that the few benefit off the work of many. Based on the rest of your comment I think we’re pretty much in agreement, but just want to highlight that as a worker-owner (vs robber baron) there’s nothing wrong with charging for what you’re worth.