If you have no way of recouping the cost of the class, the class isn't targeted at you. The most common pricing fallacy on HN (perhaps after cost-plus pricing) is the idea that every product must be targeted at all people to make sense.

So a person that simply want to learn something for the sake of knowledge is not the target of a teacher?

Not the target of a teacher that is asking for this price. There are plenty of teachers out there that can, presumably, teach the same material just as well for probably less cost to the student, however it's not the OP's job to find those alternative sources for you.

Consider that for that price, the teacher offers his time to help students.

If the price was lower, it's likely he'd have more students; perhaps a lot more. The more students he has to deal with, the less time the teacher will have to help each one of them. On one side you've got private tutoring, where a teacher can work 100% of his time with one student, and at the other end are free MOOCs with tens of thousands of students, where the students are peer-graded and are unlikely to ever interact directly with the teacher.

While MOOCs are great for what they cost, it's pretty obviously not the same quality of education as private tutoring, or by directly interacting with a teacher. So for this class, the teacher decided the minimal level of interaction he thinks is necessary to make a high quality web security course, and decided the price so that he gets an amount of highly motivated students that he can manage with the time he has.

Counterpoint: completing the course might make you a better candidate for the kind of employer that values their employees enough to pay for training like this. ;-)

Oh I'm not complaining. 2 of my colleagues just went on security training, so I think we have enough 'security experts' right now. I'd be more likely to get an android course.