Art is a special case because it's non-physical, unless it's a painting, or a sculpture or such, in which case I understand that it can be very expensive to obtain, because the artist has to spend their money on the material needed for such form of art. But in cases with music, films, novels and such things, the art itself is not a physical object unlike a sculpture. The disc or book you hold in your hand is cheap material, which you probably should pay a small sum for in order to compensate the companies who created the physical medium. But since the arts contained within these are non-physical, and simply being copies of the original work, I see no reason why anyone would HAVE to pay for it.
If I decided to make physical copies of my albums, I would probably charge the 1 euro or whatever the CD cost me. But that would be for the disc only. Not for the music.
And this is why I think piracy is OK, because you don't get the physical medium (the only part which should be paid for) when you download a film, album, or even a digital copy of a novel.