Well, I didn't "grow up" as a musician until I was about 30, it seems, and I feel like I'm still growing up. But what you describe sounds a little like Fork's Drum Closet here in Nashville. I've been growing up with them since moving to Nashville in '96. They've never invited me to the break room to eat and Gary & his wife don't refer to themselves as "mom & pop", but they know all the regulars and treat them really nice. Most of the guys working there have been there for years and they treat everybody the same way. I remember about 15 years ago when I finally felt like I had enough money to buy the ride cymbal of my dreams (22" K custom med ride), I had a particular sound & pitch in my head. Gary let me go in the back where they have scads of cymbals crammed into the shelves and pick through them. He had about 6 in stock, but none of them was the pitch I wanted. As I was leaving disappointed, he asked why I didn't find anything. I told him why, and he said he'd order a couple more. Well 2 weeks later I go in and he tells me to go check the back shelf. He had ordered about 15 of them and about 6 of them were the lower pitch I was looking for! So I felt privileged that I was allowed in the back, unsupervised, and I'm not one of the big cats in town (I'm a nobody, in fact). He deeply discounted a 70's Slingerland COB Krupa snare. I couldn't really afford his already reasonable asking price. He saw me about to walk out empty handed and basically kept dropping the price till I could afford it. I think I paid $135. I don't know if he still does it, but he used to give me a "cash" price a lot of times. Not sure I should divulge what that entailed. (And no, it's not what you think. Naughty!)
Anyway, Gary started his shop sort of the way you did, John. He worked at the music store next door in the "drum dept". It was literally a large closet area of the store & they just had a few drums & supplies. Eventually, they expanded the drum area to about an 8x10 room and nicknamed it Fork's Drum Closet. I think about 20 years ago now they were able to buy the building next door and expand. They have that place crammed full of gear.
The best and worst part of it, Gary has his Ludwig & Slingerland snare collection on a shelf all the way across the front room, up high, when you walk in. I think they're all 5x14 late 50's & 60's and I think he's got about 98% of all the finishes in the catalog covered. He won't sell any of them. He's told me he would trade for one he doesn't have.
In closing, I would like to say I despise all the big box "music" stores. They're a total waste of time. The ONLY time I go to guitar center is if I need a head or a pair of sticks and I don't have time to drive to Fork's.