We live, let's face it, in the age of the internet, when it is essentially trivial to get hold of any data. If I like a song that the radio's playing, I can, should I so desire, obtain a copy of it without needing to pay anything above and beyond the cost of keeping an internet connection active. I don't, though. Generally, I go to iTunes, and I pay money. Why is that? How is iTunes beating "free"?
The first part of the equation is ease of access. I already have iTunes; most of the time, it's running, since this machine is so over-endowed with processing power and memory as to not notice any program save some games and my web browser (thanks to the memory leak). So buying music from itunes has very low overhead, especially given that I don't have iTunes taking payment from my credit card; instead, I'm allowed a budget by means of gift cards. Everything happens automagically, and that's a big advantage. Compare the "free" method: search a stupendously large results set, some or all of which may be mislabelled. The legitimate method is giving me a massive advantage in convenience.
The second part is safety. I can reasonably assume that any music I should happen to download from itunes is merely the music, and not some horrendous foul beast that will render my computer a drooling, leprous zombie at the command of some nefarious thug-for-hire, and probably won't be the right music anyway. And if I should get infected by means of iTunes, I have redress. I have paid for a service, with reasonable expectations of what will and will not be delivered, and so I have a means of getting compensation should Bad Things occur. Again, the legitimate means has the advantage.
The third part I've touched on, but it bears repeating: there's a reasonable expectation that things I buy via iTunes will work in iTunes. Generally, they work in other programs as well, but that's not something I expect; it's merely a bonus. Anything acquired via the shady means has nothing to provide an assurance of functionality, and nobody to complain to should it turn out to not be functional. Amazingly, "paid-for" is coming out well ahead of "free" again.
What all this adds up to is simple: I'm not really paying for the music so much as I'm paying for convenience in acquiring it, expectation that it will do what it says, and expectation that it won't harm me. I'm paying because I see my time as better spent listening to the music I like than it would be spent tracking down a good enough copy in the seamier corners, and fixing any problems arising therefrom. The same reasoning applies to why commercial software I use is paid for; it's simply less hassle that way. While I COULD get it for free, there are potential pitfalls and inconveniences that I simply don't consider worth dealing with. If I feel the price of a given piece of software is too high *cough*Adobe*cough* I simply find a cheaper alternative (which can be free; the software I use for image editing, for vector drawing, and for 3d modelling and raytracing are all free, provide their source code for free, and require improvements to said source code to be freely available) or do without.
So while some would have it that only a mug pays for software, I see it differently. I see my time as too valuable to waste troubleshooting something that would probably just work straight out of the box if I laid out a little cash. This is before we go into the ethics of paying creators (an unambiguously good thing to do).