There is absolutely no reason anyone should be paid forever for labor they only perform once.
Say you produce software. You've done some labor, and you should be paid for it, I don't dispute this. But I hold you should only be paid once. Why should you be paid per-consumer? What labor are you doing for them with each transaction? You didn't redevelop the software for them. You're just giving them a copy, which costs you nothing. And they're expected to pay for it. There may be a SMALL cost to you, in the form of the medium. But why should they pay more than that small cost? It doesn't cost Microsoft any more to distribute a Windows CD than to distribute a blank CD.
You might also maintain the software over time. I hold you should be paid for this as well. But again, why per-consumer? How hard you have to work doesn't depend on the number of people who benefit from the software updates, so why should your pay be multiplied by it?
The obvious explanation, and the only reasonable one, is that you're charging for your initial labor of developing the software in the first place. Which is all well and good, but that brings me back to the initial point: Why should you be paid forever for something you only did once?
Granted, if it didn't work that way, it wouldn't be a viable business model. You have to sell things above their value, or else you don't earn a profit, right? But I question this as well. I don't question the undeniable fact that making a profit is necessary to get by in the modern economy. Instead, I question the economy itself that necessitates this. How can any economy be just, if it forces producers to cheat consumers out of their money just to get by? A profit-driven economy is a solid foundation for a society, as we've all seen, but it's nonetheless unjust. In a perfect world, all transactions should be equal-value transactions. Fair trade should be the only trade. There should be no room for doubt on this matter, yet look around you.