You got your analogy wrong.
1) If I offer a service, it's not one time - I need to keep working till a specific deadline/check point is reached.
With music/movies, it's a one time investment - You compose music once and put it on sale. And it does the work for you.
Just for comparison, if I stop providing my service/offer it for free, I may not make money at all.
2) I'm not asking 100% of the artist's money for free. It maybe only a certain (in)significant percentage because despite piracy, the artist still makes money from sales. In fact, piracy improves sales (see link in parent post).
Whereas, if I offer my services for free, I make no money at all and there is no free marketing for my business involved (that would make me profitable) as in the scenario above.
So, it's not fair that you expect I should offer 1) services for free and 2) 100% of it.
I totally get your point though, and like I said, I still believe that time and effort, one time or not, is pretty valuable.
Cheers.