What is necessary to prove reliability?
I don't think "proving reliability" for most people really means anything more than "trouble free long enough to make me happy".
There is no objective standard or definition for this.
Well, why do you think 9mm is cheapest?Most people are cheap, that's why 9mm is the most popular. It's a good market.
Technically, 99.9% of people don't need a gun.
Beyond that, there's a good case to be made for carrying the least expensive reliable gun you can get. I'm sure quite a few people do exactly that. Few of those are going to be gun people, though - and bear in mind what kind of a website you are posting on...
1. Commercial market salesWhat statistics back that up?
I can maybe agree with getting a Glock as the aftermarket is the best and you can pretty much get any part you need.
At least one thing, I can see little reason to buy a Hi-Point over Dagger or BRG9.