With guns like the Dagger and BRG9, why pay more for FN, Glock, Walther, H&K, etc?

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.

Bottom line: YOU are the one that has to be satisfied that your chosen carry will function as designed when in need.

("YOU" here, of course, meaning any individual who chooses to carry a firearm for protection.)
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.

You really hit the nail on the head. If I buy a Gold Cup I'm still going to wring it out before I use it, even though I'm sure Colt has the kinks worked out since the gun's basic design is a century old. I'll still test it thoroughly in case it's a "built on Friday" gun as even the best companies have some lemons. Certainly one's confidence in a design or company along with your personal appetite for risk will affect your decision. In some of my hobbies I could fairly be characterizes as an early adopter, but I'm not when it comes to firearms I might use in a defensive situation nor the associate accessories. WMLs are a good example. I've got quite a few Thrunite and especially O-Light flashlights but I wouldn't buy a WML from either company. They haven't been in that arena long enough to have a track record and teardowns of their hand held lights show some places where corners where cut to save money. It's telling that companies like Surefire and Elzetta rare lead the pack in light output, preferring to stick with proven emitters with a solid track record which can only come with time.

I'm an admitted HK fanboy. Over the years I've had at least twenty firearms from them, probably more. None of them have had any issues for me and all seem (subjectively by me) to be the best made guns in their respective classes. Normally if I buy a sidearm for CCW I'll start out with 200-300 rounds of ball ammo. If a new gun clear that low bar then there's no point wasting expensive duty ammo. Provided it's reliable with that I'll run 200 rounds of duty/carry ammo through it (which is almost always Federal HST unless it's a wheelgun). If it gets through those 400-500 rounds I'll tentatively consider it good to go. When dealing with a new HK I'll often shorten this to 100 rounds of ball and 50-100 rounds of duty ammo. Yeah, maybe I'm wrong and I'll die in the streets but experience has shown me that HK will almost certainly be good to go.

Certainly I've had CZ-75 and 1911 clones that ran fine. As someone upstream mentioned, those are proven designs, copied by solid gun companies. If a company that's never made guns before decided to clone a popular gun I'd probably want to know their manufacturing standards and experience. If was in the market for a Glock I suppose I wouldn't rule out a clone but it would have to clear a higher bar before I'd trust it. To be clear I'm not implying the Dagger is a bad gun, just that I'm not brave enough to be the beta tester.
I'll admit I have not read the entire five pages of posts on this topic. I've seen it before, though. It's just interesting how many gun guys can be strict economists. We often get questions that amount to no more than "if a cheaper product suffices, then why spend a dime (or even a penny) more"? It's not much different from the endless balancing of capacity versus caliber or, in some circles, obsessing over ounces to get the most lightweight and efficient gun. The answer (which has already been given, probably in multiple ways) is that people like (and buy) what they like, and some people make enough money that spending another hundred or two isn't a big deal. This is why I carry a Glock 43X when I know the S&W Shield is cheaper (I tried both; the Glock was my favorite). It's why some drive a Lexus when others drive a Civic. It's just what makes people people.
I don't think the Honda/Lexus dichotomy holds. A Honda Civic will go 300,000 miles, just like a Lexus. A Yugo will not. I would put Ruger handguns in with the Honda Civic/Toyota Corolla side - maybe not as pretty, made to a price point, but reliable and durable. Sig might be a Lexus.

The question is whether these budget 9mm guns are Yugos or Civics. We won't know until they have been on the market for 5 years or so. Me, I will spend the additional $50 for Ruger if I want an extra budget 9mm to toss in the tacklebox.
Most people are cheap, that's why 9mm is the most popular. It's a good market.
Well, why do you think 9mm is cheapest?
When I was in college in the late '70's, the cheapest centerfire pistol round was .38 Special, followed by .45acp and .357. 9mmP was more expensive than those three.
Think why it was.;)

Today 9mm is the cheapest centerfire pistol caliber because of popularity of the handguns using it.
I like variety so I've got a lot of guns in the safe. I do have 2 "real" Glocks (and plenty of other models along with 2 Glock clones). Some I trust just as much as the Glock (ie, my S&W M&P). Others - not so much (Remington RP9, S&W SD40, etc).

I will say though that my first Glock that I ever had: jammed all the time. Turns out it had a faulty extractor that had to be replaced by Glock. After that it ran fine. Bottom line is whatever you buy you need to put some rounds through it and make sure THAT particular gun works. Anybody can make a dud. Buying a more respected brand just reduces the dud-ratio and makes it less likely.
I was not alive at the time but I remember people saying that in the 80's glocks were one of the cheapest pistols on the market and of course they came with the stigma of being "tupperware guns" that some people still havn't gotten over today. Companies like PSA will have to walk in glocks footsteps for a good long while before they can build up the reputation for reliability and durability that glock has. There are some things that a dagger is objectively better at than glock. Ergonomics being the big one for me. Also just from a simple design perspective PSA has been offering stuff that people like such as ported slides, threaded barrels, cerakote colors, and optics mounting that glock has never gotten on board with despite obvious market demand. I do have a PSA dagger though I don't really use it. If PSA keeps making new models and proves to be able contend with glock and sig and S&W in the future in terms of durability and reliability, I think they will one day be sold in every gun shop in the country and be competing head to head for sales. If I take apart a Glock and a Dagger and compare everything side by side, which I have done, I can't really tell a difference in build quality or materials. The material the frame is molded out of on the dagger feels stiffer and I do wonder if that may be more brittle. I would maybe give an oem glock a slight nod for having a better stock trigger group.
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...

99.9% of people don't need seatbelts either, but in the situation they are necessary, the .01% of people will want them to work every time.
What statistics back that up?
1. Commercial market sales
2. Government market sales

With only a couple of exceptions, the LE/Mil Glock sales are genuine Glock. Clones either don't enter the competition or are eliminated early.
Glocks don't win based on looks. Reliability and price point do.

When Glock sells to LE they do so at a huge discount, sometimes at pennies over cost. There is no better salesman than being the official issued handgun of the FBI, Secret Service or the military. Adoption by LE and Mil spurs commercial sales. SIG knows this, S&W knows this, HK knows this.

Clones don't get those contracts. They lose.
I can maybe agree with getting a Glock as the aftermarket is the best and you can pretty much get any part you need.

This is pretty much why I bought an Apple Ipod, everybody and their great aunt were making accessories such as docking equipped radios etc.

At least one thing, I can see little reason to buy a Hi-Point over Dagger or BRG9.

One of the things about the Hi-Point is the slightly longer carbine magazine won't fit and work in the same caliber handgun. Dumb, if you ask me.
While I have first hand experience with over a dozen Glocks, I have first hand experience only with two Daggers. Nothing indicates that they are inferior to Glocks but when it comes to accuracy, neither Glock, nor a Dagger would be my first choice.

The thing with these clones to consider is that the maker can "stand on the shoulder of giants" so to speak.

Glock does all the engineering and testing. Copy their specs, improve on grip shape or sights, and charge less.

Raw material wise I've always heard a glock is about 80 bucks to make. There is profit in polymer.

I wouldn't have qualms about using something built off their tested designs.

Heck, even a glock isn't really a glock. Remember about ten years ago when the gen 4s came our and there were issues?

Prior to that 2012 and before gen 3s used tool steel or cast parts. Glock went to mim and had issues.

The big Vegas ranges say the gen 1-3 used to rack up these massive round counts between parts failures, 100-300k rounds. Glock is built on that reputation. The new glocks since material changes tend to go more around 40-100k. Still good, but...