I am also shocked when I see teachers asking $40 a lesson or more, regardless of country...and I'm a language teacher myself! There are wealthy people in the world, but how many of us can afford THOSE types of prices, even in so-called 'rich countries'?
It's the same problem a person has if they open a business. Do I sell luxury items to only a few people -- and charge A LOT for each item? Or do I sell discount items to a lot of people -- and charge little for each item? What will make me more profit in the long run?
Answer: it depends entirely on how much cash you already have, and how much you want to work (= how many students you actually want to have).
I am a bit surprised that Italki members living in developed countries find shocking that a teacher asks 40 or 80 dollars for a lesson. But language teacher are not volunteers in a non profit organization. They are professionals that usually have at least a bachelor degree from college, some have even PhD.
Why should they earn less then a skilled labourer? Here an example of the fees of a plumber in the States:
The average cost per hour for a plumber ranges from $45 to $150 per hour depending on the job, timing and location.
That said, I appreciate to be able to have many lessons at a competitive price here on Italki. I couldn’t pay 80 dollar for each lesson. But I do not feel shocked if somebody asks this price, he surely has good reason and Italki is not a charity organization.