You do not say where you are from but this kind of stuff is the reason that I'm an independent DM. I stopped being affiliated with one shop for reasons like this and the fact that as I also am into technical diving I choose to dive the same configuration in open water all the time. Whenever possible of course. On vacation I may not use doubles but I am in BPW and long hose. I have a jacket style bc and use it with a conventional octo set up in the pool but on OW dives At least for the last 5 classes I've assisted with for two different instructors(PADI and NAUI) I've been in doubles with BPW and long hose. My NAUI instructor actually encourages it because he's also my tech instructor.

The more time in doubles the better. Even if it's not the brand he sells (my stuff is DSS, he sells dive rite) I have enough accessories from him that he was not going to make me go out and buy all new gear when I already had two BPW set ups, 3 regs, etc. This sounds like a shop that is desperate for business to the point that they are charging you to be a walking billboard for them.:no Go to them and say fine when with you I'll use your rental gear, When diving for myself I'll use my stuff. If they say no, find another shop and tell them to go stuff it. This is the kind of crap that creates DM's who may be very good at what they do but get disgusted with the politics and say screw it. If you were their employee it would be different but you are paying them. This is the big catch for me. It's also why certain agency policies and marketing practices are pushing me away from that agency. It's all about making money for the agency and shop. Screw the DM. It's really not a professional rating like it should be. It's a way of getting more money and cheap labor. It's designed to push DM's into instructor courses to try and recoup some of the capital they've invested in training and bring in even more money for the agency.
I've been saying this for awhile- If we have to pay insurance, dues, have the latest gear, etc. why are we treated in many cases like slaves with no pay, maybe free air, and so-called "key man" discounts that are worthless if we don't need any new gear?

And is a discount of 15% really anything if the original markup is 150-200% or more and the guy on the street who does nothing to help out gets 10% off. A real discount would be 10-15% over COST for those of us who bust our asses, volunteer time, resources, skills, and do our best to make sure the students come back alive.
Problem is it will never change until we can get together and say in one voice we are pro's, we expect and demand compensation and encourage DM's to be to do the same. I myself am guilty of perpetuating this abuse by continuing to work for some of the same things. But if I want to dive and even have a chance of making a few bucks it's a necessity for now. But the thing is there are courses we can teach without a shop or instructor and with a little creativity and the right contacts it's possible to make a little cash for ourselves

. PM me if you want to know how? I have a few things in the works that in the next couple months will be paying off. This is not a pitch to sell something. I'll gladly tell anyone how I'm putting my own programs together that while not getting rich will give enough to cover some of the costs of being an indentured servant, I mean DM. In the meantime don't give in to the hype and BS about what they want from you. Again you are paying them to teach you, not abuse you.