When you buy a rifle, you're paying for certain features. When you buy the hobby grade (lower end) or mid-grade rifles, you are typically saving money by omitting features that the top tier rifles include. When you buy top tier rifles, you are buying the total package. You have the best quality components, the most consistent and often the highest quality standards, and usually the best warranty. Essentially, you have the best base platform to work with. It doesn't always have to come down to "would I take to war?". It's often as simple as "buy once, cry once".
There are a couple philosophies that seem to pervade the AR world.
One is the "upgrade later" philosophy where people say they'll save money now by buying a low end rifle, and then just upgrade components as they go. In the end they spend a lot more money "chasing the dragon" as it were, and eventually they realize that they could have saved money and headaches by just ponying up more from the start.
As an example, let's say you want a Ford Mustang for a drag racing car. You can save money up front by buying a base model V6 and then just upgrade as you go to say, a supercharger, suspension, brakes, exhaust, etc. You wind up dumping another $20k into the car, when in retrospect it only would have cost you $10k more to just upgrade to a GT w/ 5.0 V8, and you'd have the same performance as you did AFTER dropping $20k on the V6.
Another philosophy is the "I'm not fighting with it" mindset. That doesn't matter. My wife hates that I drive a BMW because she thinks it makes us look rich, and we're not. Only rich people should own BMWs, and it gives a bad impression to people. I drive a BMW because I love to drive and occasionally track race, and this is my 3rd BMW. Wife has hated every single one. Her mindset is completely illogical (aside from just being a woman in general

), because I'm not a pro race car driver and I'm not rich. When I drive, I want the best driving car there is for my money, and IMO that's a BMW. Same thing applies to guns. You don't have to be professional gunfighter to have a reason to get a high quality AR. Just like you don't have to be a special ops sniper to own a Zeiss Hensoldt scope, or a competition shooter to own a $5000 custom 1911.
A third philosophy is the "just as good as.." mentality. People out there do contend that a Bushmaster or RRA is just as good as a BCM or Colt because they look the same and the primary forgings in the raw came from the same foundry, or whatever. Here's the deal, the Toyota Corolla and Lexus IS are essentially the same car. However, if you spend time in both, any person would conclude that the Lexus is a far superior car. When you know what to look for, you can see the differences between the good brands and the mediocre brands.
Lastly, there's the "my buddy owns ____ and he's never had a problem with it" philosophy. It's important to differentiate between anecdotal evidence and known reputation. Last summer at a shooting course a student was pretty confident in the performance of his new DPMS carbine; that is up until it went Tango-Uniform halfway through the morning of Day 1. The top level brands that have been presented (BCM, Colt, etc) have verifiable quality. Other brands are a lot more contentious.
Food for thought.