Arnaud,
I hope I didn't offend you by suggesting
Sport Chalet and in no way am I just advertising.
It sounds like you had a bad experience with an instructor, and unfortunately there are bad instructors in just about every place you look, as well as many good instructors.
As for selling gear, every shop aims to sell, otherwise they would not exist. Afterall, we do live in a capitalist society.
Let me explain why I suggested Sport Chalet.
I took my open water class at a small mom and pop shop in Cypress called Scuba Toys and I was very dissapointed, I almost gave up on diving. The rental gear was terrible, leaking bcd's, torn wetsuits, and freeflowing regulators. Although the instructor was okay, everything else was not.
About a month after completing my open water course, a friend suggested that I take an AOW class through Sport Chalet with him, and I did, then my whole outlook on scuba changed. :07: I now love it and have logged over 300 dives.
I suggested Sport Chalet because I took several classes there and was very pleased with the service, professionalism, instructors, and the quality of their rental and sale gear. In addition, they provide DAN insurance for their students while they are students.
So of course every dive shop is trying to make money, and you will spend some if you are going into diving, but this is why you have to shop around and get the best you can for your buck.