I had a similar experience with my LDS. Went into the shop and told them I needed to buy two sets of gear beyond mask, fins, and snorkel. After he priced out the regs and octos with computers, (Scubapro again), he price was so high he had already exceeded my budget and I left the store to "think it over". After doing a little research, I was convinced he only showed me the Scubapro since I couldn't really "shop it". I know it's a fine product, but he never even showed me another line.
Went online and found he too, was charging full retail. At the end of the day, I wound up buying Oceanic anyway, but paid less for two sets including BCD's and snappy Apollo fins for less than what he quoted on just the regs. The regs were similar to the Scubapro in feature and benefits. In short, I gladly would have paid him 20 to 25% more just to have the convenience of going back so he could explain the computer, or help me adjust the regs, etc. The price he wanted for that "warm fuzzy" was just too high. Escpecially since you can not only buy gear online but such a wealth of information about it is here on the boards. I don't need him so much when I can post here and the Oceanic rep answers my questions about my gear in a few hours.
About going back in and renegotiating with him, it was never an option. Once he tried to gut me on the regs I didn't really want to pursue a purchase with him. And as far as his overhead goes, I get that. Everyone's gotta make a buck. But these guys really have to look at their business model and rethink thier ideas about the "hit and run" high net sale vs. a long term selling relationship.
Disclaimer: I'm probably going to get hate mail from every LDS, this was just MY experience, and I'm sure there are thousands of guys out there doing the "right thing" for their repeat customers and former students. Mine didn't.