One of the things you will need to learn is how to assemble and configure your equipment.
This is where the LDS the OP talked to blew it.
Every time someone walks up to you with a problem they need solved, you have a chance to provide them with a good or service that either earns you revenue, loyalty or preferably both.
As an LDS you are competing with the Internet. That sucks if you are trying to compete based on the lowest price for globally distributed hard goods. Price has been commoditized. So you need to find a way to charge for things that the Internet can't provide competitively (at least not yet).
What do you have, as an LDS, that the Internet doesn't have? One thing is in-person service from qualified people. That translates to time, peace of mind, expertise, human interaction and community. You need to get as many people into your shop as you possibly can and give them great personal service that you can charge high margins for.
In this specific case, why not do the following?
"Hey, we could just set this up for you, and that normally costs <foo>. Of course you took OW with us, so that means you automatically qualify for a 10% discount on all gear service, even if you bought it somewhere else. But if you go that route you're not going to know how to do things yourself, and then if you need to do anything with your regs when you're off somewhere, you're at the mercy of some pot-smoking teenager.
So how about we sign you up for our next "regulator theory and set up" class? It's Saturday from1-3 and it's only <bar - which should be a lot more than foo>. Bring your buddy and then the two of you can test each others setups in the pool. If you need it faster we can do the class any evening you like as a tutorial for you and your buddy. That's a great solution because you get your own instructor and we can make sure you really understand everything completely - that's <foobar - At least twice what bar costs>.
And the next time you're shopping for gear come by, we will try to match published prices from established retailers and no matter what we'll always do the setup and testing for free on the same day you buy it. Then you'll always know you're leaving our shop ready to dive when you shop with us."
And of course if you don't have an AOW instructor and travel agent who happen to be at all your gear setup classes, and you don't happen to let them offer a couple of killer deals, and you can't find a way to encourage some really experienced local divers to show up to help with the class and talk about the awesome local dives they took with you last week and the trip they are doing with you to <somewhere awesome in the future> then you're just not doing it right.