The difference between “Selfless Masters and Paid Instructors” is exactly what 8step has said. The key word is “Professional”.
A Professional by definition has made teaching kung fu his life’s bread and butter. He does not always have the opportunity to pick his students.
Conversely, a teacher who does not seek to make his kung fu pay the bills can proceed as he wishes.
Is one more valid than the other? The answer lies in your own training. My best friend studies at a big local school. To him, it is not important who was the master’s mother’s brother’s sifu. He trains hard. His kung fu is strong. I study alone. It is important to me that I learn everything about my art, history included. My kung fu is OK. 
We both love our situations, and envy a little of each other’s.
However, I do have trouble being objective, since my training falls in the former category. Because of mindset, most people here and yes, now in China, will never meet a true master, let alone study with one. I see it every day. No one thinks of spending TIME to learn, they only think of spending MONEY to learn. “How much do you charge?” is the first (and last!) question. My master simply smiles.
Many here do not share as deeply the relationship values of respect, loyalty, selflessness and honor that come from a selfless, undistracted, previously cash-poor society. This is not to say that a student cannot go to a school, pay monthly, train hard, and learn good kung fu from a great master. IMHO, nuances between teacher and student may be lost when an art is transferred with such tender so easily acquired.
A big part of carrying on an art to the next generation, like a child, involves deep commitment and responsibility. Traditionally, there was a tangible barter relationship between teacher and student. A man’s gotta eat. The other side of the coin was how much the student gave of himself. I believe the teachers who speak out here must be of this kind. I hope it is the case.
We should feel lucky, not constrained, to be in so rich a society. Think how many masters are out there who are making a living with businesses, yet have good kung fu! Like anyone with a life’s passion, they DO want to share it. All you must do is love it as much as they do. Maybe that’s the hard part.
“Waiting is bad.” - Musashi