This was not the only disappointing gun shop in Miami. I used to buy guns at Garcia's National Gun. I bought a Smith & Wesson 686+, a Desert Eagle .50 AE in hard chrome, and a few other things. I believed in supporting local stores and trying to develop a relationship. They never remembered me. I could have bought a Sherman tank, and they would not have remembered. They always treated me like a number. They never acknowledged me when I came in. Maybe it was because I wasn't Cuban; that happens a lot in Miami. Anyway, I gave up on them and started buying wherever was cheapest. They weren't rude. I just felt like they didn't care at all about my business.
There are a lot of nice people among firearms enthusiasts. And a fair number of jerks and kooks. I shouldn't complain. They're much better than the obnoxious prizes you come across over and over in saltwater fishing.
Of the two gun stores I go to, and it's not like I'm in there every week, but I'm remembered as the guy who gets a lot of transfers by certain employees. When I'm there, if it's not busy, I always talk to the guys behind the counter about general shooting stuff or what its like living in states where NFA stuff is legal and I guess they like the conversation as it's intellectually stimulating.
I think the issue you had in not being remembered is your in a huge city, the shops get hundreds of customers and can't remember people. It's not about what you buy, it's about how you interact and how often you go there to interact. Just a few minutes of conversation with the same guys once every few weeks will make you stand out.
It doesn't work for every shop though. There are some that just don't want to be bothered if you're a first time customer, if in the first three times you've gone to a gun shop and you don't feel welcome, there is NOTHING you can ever do, no amount of money you can spend, to feel welcome.
To build up that rapport, it takes about a year to get to that point, but once you reach it, it's a great situation for both you and the store.
As for the nice guys and jerks/kooks, I chalk the kookery up to that was the mentality they grew up with 30-50 years ago in firearms and old men set in their ways aren't gonna change.