Teachers on italki can do whatever they want, because they work for themselves and italki is just a platform on which they sell their services. italki has no reason to set rules limiting how often teachers change their prices.

Some teachers keep their old prices for old students to show appreciation for the students’ loyalty. But ultimately, that is up to each teacher.

Just based on what you wrote. It doesn't sound unfair to me. It would depend on how many students the teacher has. How long the teacher has been teaching on Italki. Some tutors/teachers increase their price every few weeks or every few months depending on how many students/lessons they've had. Just like another reply mentioned tutors and teachers can do what they want in regards to their prices. You can't really expect all tutors/teachers to keep the same low prices for years right? Plus if it's a teacher, they might have qualifications that warrant an increase after some time passes. If that teacher isn't affordable anymore then simply search again or look for a tutor. Some tutors tend to charge less than some teachers.

Maybe your teacher is doing the opposite of what you are saying. He’s looking to keep only his serious students and therefore he’s increased the price.

Would you say the same thing if he decreased the price?

Well it depends... it could be because the teacher had been teaching with those prices for a year!! It just councided with your second week!

I suppose you Sed do the same.Im a serious student and I have decided to give lessons for all the summer with that teacher but if the teachers can increase the price when they want the students can not program a long group of lessons since you think in a budget and then it changes later