Take as evidence iOS jailbreakers who do it so they can download $0.99 apps for free. There are plenty of people who are never going to pay anything if they can get away with it.
Well sure. On the other hand, look at iTunes. Before iTunes Napster et all were wildly popular. Then Apple starts offering downloads at $0.99 a track and suddenly they're making a ton of money and the music filesharing sites seemed to lose all traction. Lowering the price may not have solved the problem, but it greatly reduced it while creating a revenue stream that wasn't there previously.
There will always be those who won't pay, granted. With that in mind, the question becomes one of how much do you want to penalise the honest Internet users in the vain pursuit of an unobtainable absolute?
If you think for example that a computer game is too expensive and you pirate it, surely you should put the amount that you think is correct in an envelope and send it to the producer of the game? How many people are doing that? Everyone else is just lying.
Well, if someone was to illegally download a game, they'd be foolish to provide paper evidence of the crime, so to that extent I suppose it's understandable. On the other hand, if the game creators established a channel for this to happen safely, they might be surprised. I mean that's the basis on which Humble Bundles operate and I gather they've frequently been quite successful.
Granted, it's the publisher's decision whether or not to offer work on those terms, but you can't really claim it never happens or that it never works.