The PC is certainly seen to be less profitable than consoles, which is why it's given a lesser priority.

For multi-platform titles, typically 360 and PS3 titles are developed in parallel. Often the PC version comes later, after the console releases have finished and a small subset of the console devs have time to polish the PC port.

Usually two reasons are given. One is that it's not worth the extra management complexity and dev time to release at the same time as the PC. The other is that the piracy rate on PC is so high that launching all platforms at the same time actually cannibalizes both PC and console sales.

PC games generally cost less at retail, but manufacturing costs are lower and no subsidies go to console owners. Dev costs are slightly harder due to the challenges of developing for a wide range of hardware vs two fixed targets. I think that the profit per unit sale is slightly higher on PC than console (I could be wrong).

Yes, absolutely. The fact that PC sales are normally very low (around a tenth) of console sales for the same title and games without multiplayer are pirated at a much higher rate than multiplayer games is common knowledge and entirely uncontroversial within the game development industry, and always factors into decisions about how much money to invest in PC titles. Pretty much all the major shifts in PC gaming since the late '90s - cheap console ports, the emphasis on multiplayer, MMOs, Steam, etc - have been responses to piracy.

So you're saying that since the difference in PC game sales versus consoles can be accounted for primarily by piracy (not difference in demand), and that PC game sales are 10% of console sales--that 9 times as many people pirate PC games as buy them?

That doesn't take into account that many of the pirates wouldn't have purchased the game if piracy wasn't an option. If we consider that, then we'd need many more pirates, maybe twice as many (18 times as many pirates than purchasers in total), to account for the lower PC sales.