Well, the research and the researchers are all almost entirely funded with public funds from around the world. The fact that they are forced for professional reasons to funnel all their work into a for-profit publishing industry for distribution is a historical anachronism that dies hard.

In a broad sense, there's only very weak analogy to music or film piracy in terms of the process of creative work. Everyone has already paid for scientists to do this science. Scientists and institutions have even paid the journals to publish their work in almost all cases, and they won't reap any reward if you read the work through the legitimate distribution channel. You only pay the publisher, not a starving researcher.

Personally, I'd feel very happy if someone read my papers by any means necessary. That was the whole point of writing them, setting aside the practical annoyance of simply trying to keep my career afloat.

Edit: The lifetime value of a single paper to the journal can actually be priced, since they started charging researchers for open access a few years ago (often in addition to other fees). This number is usually in the $2-5K range per paper, in my field.