I'm afraid your analogies fail as well, and I think the post reading one does work. Here's why.
On the sideshow ride, there is no way to know, when you sneak on, if you'll be taking a seat from a paying customer or not. The important difference, though, is that it's possible you would be at all-the number of seats on the ride are limited (scarce), while the number of copies are essentially unlimited (non-scarce). That's why you can't compare copies to ride seats, or candy bars, or anything else that's limited in supply. With these marvelous machines capable of making copies at high speed of anything that can be digitized, copies of any digital information are no longer scarce, unless we artificially make them so.
Your second analogy is that of, essentially, a verbal contract between you and I. You began work on my car specifically because I promised you $100 for it. If you complete the work satisfactorily, and I stiff you on half the money, that's fraud and breach of contract.
However, that's again a flawed analogy. No one from Dreamworks called me up to say "Hey, look, we've got this great movie idea, but we wanted to negotiate what you'd pay for it before we start work." They didn't begin work on it at my request, or based on a contract and promise to pay from me. A more appropriate analogy here, to go back to car washing, would be the guys in New York that come up and start washing your windows without asking, and then expect payment. They didn't begin their work at my request, and I'm under no obligation whatsoever to pay them-I never made an agreement with them. If they do a good job, I still might out of being nice, but I'm not obligated. And that's where you say they "demand" payment-well, yes, some of them do, but in this scenario, I'm under no obligation to oblige them. Asking nicely will work much better than a demand in that scenario.
That's where we're back to the "reading the post" analogy. The person who made that post didn't contract with me to read it after it was finished. The author of that post has no obligation to pay me just because I say so. Similarly, a person who makes a movie, writes a book, etc., doesn't do so under contract with me. If I enjoy them, I probably will "drop a couple bucks in the guitar case," unless they become so obnoxious and demanding that I don't want to give them a nickel.
I generally will pay for things I like, if they're made available easily enough and without onerous DRM, and they're not through an organization pulling these shenanigans. As you said, it's not always lost sales. Several years back, my sister burned me a CD of an independent band she'd come to quite like. Well guess what? I came to quite like them as well, and since then have attended several of their shows, gotten a couple T-shirts, recommended them to others, etc. If not for that CD, I probably would never even have heard of them, and even if she'd just mentioned them, it probably wouldn't have been enough for me to seek them out and pay for a CD. Did she harm them by burning that CD, or do them a service by giving them free publicity?