2. What are the benefits for a diving center to develop nitrox or trimix class ?
2.1 What are the success conditions in order to develop this ?
I live in a specific area where there is not much call for either nitrox or trimix. The local diving is too shallow, and much of it is univiting to all but the most active scuba enthusiasts. Thus, when we use nitrox, it is usually when we travel to other locations. It is not that people are against nitrox. We have a lot of nitrox certified people here who use it when they fly to vacation spots. We don't have many people who are trimix certified, though.
It is therefore not very advantageous for local dive shops to do a lot of work with either nitrox or trimix. Our shop deals with it, but in a very limited way. The shop buys large tanks of oxygen and helium ato make the blends that a small number of people take with them. I am one of those people, and I just got back from the shop where I blended trimix for a trip we are taking this weekend. We will drive about 6.5 hours to get to the only place in our region where we can use it, and we will have to take big tanks with us to make our own refills out of the truck, because there is no place to get it where we are going.
So you can probably see that our shop does not make much money on this. They do it because they want to keep this part of their client base happy and diving. They also do other things that help us out and bring them no profit, like letting us store a lot of our equipment on the premises so that we are not having to lug steel doubles around too much. By doing so, they keep us loyal to the shop. In gratitude, I buy my gear through them, even though I can sometimes get it cheaper on the Internet.
If we were located somewhere else, things would be different. In some places in the country, nitrox is so popular that shops keep large tanks all blended and ready to go. They will use expensive mixing procedures that work best when you are making large batches. (We use partial pressure blending because we don't have enough use to justify the expense.) If you have enough interest, then the shop can make a profit from it.
As far as trimix is concerned, a benefit to being the only dive center in your area that deals in it would be that the relatively small number of people who use it will flock to your center and create a new client base for technical diving equipment.