How many lessons to pass the B1 test?

You are likely to need about 150 TU teaching units (TU) with me to pass a B1 test, if you are serious in doing your homework.

The Goethe-Institut estimates 350 TU in a group class for achieving the same.

The Warendorf Volkshochschule (adult education) consider it as an „excellent result“ if after 660 TU (!) about half of their students pass B1. (Sorry, this link exists in German only.)
Even if their students were less used to learning than the Goethe classes, such a result cannot be explained only by this factor.
150 TU cost 6900 Euro with me. This is the price for a used small car in Germany. I think the use of a small car can be really compared to the use of a sound knowledge of German.

Different from a car, your knowledge of German cannot be stolen. You won’t have any consequential costs like insurance or fuel. And it won’t get worse but better by use! There is even more, lately they found out learning foreign languages even helps to prevent dementia!

And of course it’s a great feeling to be able to communicate in German fluently.
Please consider that the price for a lesson has to pay for preparation, taxes, sick days, holidays, time spent on accounting, teacher’s further education. What can a teacher offering dumping prices realistically offer you? Good education is simply worth its price.