I suppose it really depends whether you are running a business, or a lifestyle choice.
If you're running a dive business, then if you're selling the same as everyone else I'm afraid it's the same problem as any other retail business. Motorbike shops have pretty much all gone to the wall leaving a few big players as people go in, spend an hour trying on the kit, then bugger off and buy it off eBay or from one of the big box shifters. Anyone sells Apeks/Scubapro etc so it's just a matter of ringing round and playing "but they are doing it cheaper" game. It's a bloody hard market to be in as there will always be someone who will do it for next to nothing. I remember when you could call round the shops and get a brand new 12L Faber for under £90.
The other option is to specialise and say "bollocks" to the box shifters. Kent Tooling does this- they make a superb product but you will only see them in a few dedicated shops who stock quality stuff as they have quite rightly decided to protect their margins and reputation. Then again they have another string to their business so aren't completely dependent on the reels etc. Ditto O3- you don't see many retailers for their suits.
What a diver wants (a shop like UE) and what makes the margin (a box shifting shop) are 2 different business models. UE have dug out an enviable reputation for stocking the top end stuff and divers are prepared to pay a premium for this. The box shifters are all competing for the same leisure pound and the only thing they can really fight on is margin.
Before the Internet, the October dive show was where the shops would get rid of their end of season stuff at bargain prices. It's not been like that for years now. I was after a pair of Quattros and they were cheapest at Decathlon!
I have an online credit check service and if you punt in the details of the companies in the industry, the only people making and real money are the big manufacturers and importers.