I am also not trying to sound like a know-it-all, but i'm sure that each of us have walked into a business (vape or otherwise) and thought to ourselves "how is this place still open?". I am referring to one of those places. I believe that the answer is the location. Think "Central Place Theory". His store is probably the closest shop to 100k people's home or work and that alone has propped up his store.
I had discussions with the owner of this business as I was looking to either buy him out or start a new shop in the area, so I've seen his books and heard his story, unfortunately he wanted too much. Removing 50% of his sales by offering his customer's a similar assortment of products, at a similar price, and in nearly the same location from a clean, well stocked, and friendly establishment will remove his ability to make payroll and rent.
I have also been in the other shops in the area and there is no doubt that running shop the way that I plan will lure away some of their customers.