there are many who do not much respect what was taught, even they live from it, to say putting "higher proposes" over the teachings themselves (virtue). The thing is, one does not need to take part on it. But as long as one is in a ordinary mundane circle, money or other back-gifts are well used to keep dept and gratitude balanced. Sometimes payment is also a first step to teach gratitude, thinking on the countless Dhamma-vampiers who would never have the idea to pay something back, who would grow heavier and heavier till they are pulled down by their dept. So there are also those adequate to mundane ways, who sell paper, something we can look at and touch.
It's always important to see things from one's own intention and Dhamma does not carry any rights (like in this case: "I have the right to get Dhamma" or "Dhamma must be free"). If your situation gives you access to given Dhamma or not, depends also on your own merits. That is why practice starts with Dana. Not only to learn letting go of possession, but also to make the possibility for being able to receive bigger.
To understand the way it was thought of the Buddha (a wheel out of worldly dept) this two essays are very useful:
Thing's one really owns, one would not sell, because he would know that they are not buy-able and to cheat (or in-honest livelihood) is far away of his intention.
Just that! *smile*
BUT! it is important to become a real Buddhist first. Like Punna did: Nate sante baram sokham _()_