Just to be clear: people are stating that their knowledge and time are worth something, and want to ensure students will stay by charging them money.
As a student...don't you think MY time is worth something? Okay...I pay you for your time and attention and knowledge. I hope you didn't want more...like respect, or gratitude or good attendance or long term committment to your school or art. After all...you get compensated for the time...whether or not a student shows up.
And another thing...just be clear that YOU, as an instructor don't 'get' anything from your students other than cash. Because if you need training partners to keep your skills sharp, or long term students that advance to the point that YOU can work your art...then you are taking without compensating. How do you even THAT out?
You've got a valid point, but it seems like you've buried it under a posture of entitlement and demand.
This thread is about charging students for the training provided. Sadly, many to most of us have found that too many students squander what we give them if they don't have to pay for it in some fashion. Let's leave the true professional instructors off the table for the moment; obviously, they must successfully balance the demands of the market with their desire to teach, and it ain't easy. The instructors like me who have full time jobs still have costs... Some of us can absorb the cost of instruction (perhaps rent, insurance, equipment, etc.) -- and some of us accept that it's going to be a bit of a financial burden. Hopefully, the burden is reasonable in light of what we get out of teaching. So, we do expect students to contribute to the costs of their training in some fashion, instead of simply "giving it away."
To expand on that a little -- I only offer one formal class a week. My experience has been that if I offer more classes, no matter how much the students scream for more classes, they don't show up. They start making excuses... But with one class, they value that night and that time and don't miss it. Draw what conclusions you wish.
But, as I said -- you do have a point. It IS a two way street. I've seen people who teach solely to have a pile of sparring partners... Sometimes, they end up with a few good students, but that's not their purpose. If it's clear that's what they're doing (like running a gym as a pro or semi-pro fighter), no problem. That's honest. And, in truth, that's what the instructor owes the student.
Honesty. Honestly and fairly offer the art to the student. Honestly encourage and teach them. My goal is for every student to make black belt -- but the reality is that some never will achieve a black belt. If, as a teacher, you're honest with the students, I find that they'll in turn be honest with you, and give you their best efforts. I do expect my students to teach me... because, in breaking things down, and sharing them with students, I learn more about my art. I want my students to be honest in sparring with me; try to hit me, don't simply assume that "the teacher is too good to be hit."
Respect? I expect my students to respect the fact that I'm the teacher, in that training hall. If they don't respect me -- they shouldn't be training with me. I expect them to respect those I bring in as guests, because they respect me. And I respect the students in return. I respect their time and their effort and their dedication -- because without students an art will die.
The biggest problem I have with your post is that you see a purely mercantile approach; you pay your dollar, you get your training. Teaching anything is never successful as a purely mercantile proposition like that. I can deliver you a package for $x. I can build you bookshelf or cabinet for $y, and simply give it to you. I can't give you knowledge in the same manner. The sharing of knowledge is a two-way proposition; there's no way that I won't get something back from teaching you, beyond the cash. You'll ask a question that makes me realize something new; you'll be moving as my opponent, and I will get the practice and chance to see things. Even the most sterile of learning environments, like writing a book or preparing a videotaped lecture, forces me to re-examine what I'm doing, and figure out how to explain it.
Let me use an example from the class I taught last week. I was working my students on their front kicks, with everyone taking turns holding the pads. While teaching, I took turns with the students kicking and holding pads. Holding the pad, I could feel things about their technique -- just like they could feel things when I kicked the pad they held. But I also had to watch them... Well, along the way, we noticed that something was off in MY kicks! It took a couple of us looking, and it was a problem that several of the students were encountering, as well. We solved it -- and we all learned (or rediscovered) a piece of the kick. Did they get what they paid for? Did I get more than money in return for teaching? Was it an unfair transaction?
IMHO, there comes a time when we should give something back. Now, it could be said that you're giving back by teaching for money, and yes, that is true. But in this case, you're doing something nice for people who can't afford much. Their 'payment' IMO would be their dedication to you, and the lessons that you teach. 
