As one of the principals in a Pattaya dive shop, I wanted to share my opinion regarding pricing and discounts. My partners' opinion might differ, but I don't think by much.
My first rule is that discounts are given when deserved, and that usually means they are given only to good customers. It's a two-way street. You help us, we help you.
That means if you come in with a couple of people, buy more than 1 course/trip, buy some gear to go with your diving, or have some sort of combo of courses/materials/trips/gear, then, sure, we're going to be pretty generous.
If you come in out of the blue, make it obvious the only commitment you have is to one purchase and only to the shop most willing to undercut others by the largest amount, then you're going to find me less than receptive to haggling.
Pattaya dive shops historically have worked together to stay away from the price wars elsewhere that have resulted in 6,000 baht, 2-day Open Water courses. Recently all the major shops here raised prices for day trips in unison to offset the incredible rise in fuel costs. It was the first increase in 3+ years, by the way.
Most shops also have comparable prices for courses. Open Water runs ranges from 14,000-16,500 baht including materials. Advanced ranges only from 12,000-14,500. I haven't surveyed Rescues recently, but I think most people here are disciplined enough to keep prices in a range where they are fair to the customer and help sustain a safe and competant dive center.
Slashing prices helps no one, INCLUDING the customer. In diving, as in anything else, you DO get what you pay for.
Here at Aquanauts, we charge 12,000 baht (and have for 3+ years). The book is 2,100 baht (below PADI recommended retail, by the way.) For that, you get 3 days of training, local pickup/return service, a freshly cooked, multi-course lunch, soft drinks (no extra charge, equipment rental (if needed) and your certification. You do the theory in a modern, well-equipped classroom with up-to-date materials. You dive on our own, non-shared boat with instructors we trained ourselves.
And, as for the training, we take Rescues very seriously, as they are a huge part of our instructor training program. Month in and month out, our IE candidates score 5/5 on rescue on the Instructor Exams. During DM training, we drill them repeatedly, having them perform rescues in an annotated fashiion, calling out each step to increase memory retention. On the just completed IE, in fact, the Mermaid's Course Director was evaluating our candidates for Rescue (examiner was short-staffed) and my partner told him that if any of our guys didn't have the pocket mask on the "victim" in 10 seconds they should be failed.
It was a joke, of course, but pretty much what we expect of all our rescue students.
So, sure, you can hammer on people and pit one shop against the other to get the ultimate low price. Or you can place the emphasis on where it properly belongs, being the quality of training and facilities, the customer service, the the boat, the upkeep of the tanks and gear, the number of Thai staff on hand to assist you and the overall enjoyment of the experience.