What can't be ignored is that 4 of the top 5 PC games pirated don't have a demo (correct me if I'm wrong), and so many people turn to downloading the full game to try it, though I imagine a lot have no intention of buying it.
Illegal torrents seem to be being clamped down on nowadays thankfully, and people should realise it only makes the full games more expensive and less PC releases emerge.
There was a time when I may have thought about pirating the most expensive PC games, such as COD4 or MW, but that's only because they charge silly money for them new. As a PC gamer I'm used to spending quite a bit less (I know consoles are different). However, the expensive games are almost always over-hyped rubbish anyway now. Best game I've played in the last few years is probably Fallout 3, which has been priced very sensibly on all platforms imo, and probably benefited from it.
PIrating games in no way makes games more expensive, games have sold at similar levels for a long time. Many hundreds of millions of people have pc's, not everyone games, not every gamer buys every major release, its impossible to say how many people will want to spend money on any particular game. Set the price too high and less people buy it, its really that simple. Theres been no slow down in release of pc games, theres a profit to be made, it will be made, its really that simple. COD MW 2 made a killing in PC sales, they'll continue to release games as long as they make profit, which they do with ease, as all decent games do.
Crap games don't sell well regardless of pirates, likewise good games sell well regardless of pirates. Many pirates download a game so they can play it at the same time as everyone else, and have still bought and are awaiting the game. Fallout 3 was no more or less expensive than any other game on release, for as long as I can remember 99% of games launch between £18-26 on preorder, with one exception that I can remember in the past 5 years(cod mw 2).
Price has nothing to do with it, at the end of the day people can't spend an infinite amount of cash on everything, once they are tapped out, most people will either never ever play a companies game, never pay for it, or maybe download it, play it and have basically stolen nothing.
The numbers are also skewed, heavily. Theres zero point for most people to burn a game for a pc and share it with other people, its a waste of time, effort and money, everyone can just get their own copy. For consoles, thats not true, you have to burn the media anyway, so one friend is far more likely to download a console game and lend the disc to friends to play.
Likewise on both platforms, downloading the material doesn't equal lost sales, nor people who actually played the game, nor people who haven't paid for a game. All 4.1million pc version downloaders could all have ordered the game, and all the 360 users could have downloaded and shared it with another 15 million xbox owners, the numbers themselves indicate nothing in regards to who downloads more on what.