One of the factors that many don't consider is the age and eyesight of the shooter.
@Fig touched on it but it bears a decent explanation.
I'll use myself as an example.
For most of my younger life, meaning 40 and under, I had perfect eyesight.
I'll clarify that by saying it was much, much better than 20-20.
I could see and identify things that others needed quality binoculars to see. Birds, animals, fish in the water, it didn't matter.
Shooting groups at 100-200 yards with 2x pistol scopes and 1-4x rifle scopes was no problem at all.
Fast forward to turning 41 and I start noticing squinting to see things. Scopes needed refocusing, etc.
I go to the eye doctor and get checked out. His response was that he didn't understand what I was bitching about, because I was slightly better than 20-20. I don't remember the exact number but I think it was 20-15.
I told him if that was normal vision, it sucked. I remember him saying if I didn't like that, I'd really hate 20-20.
He was right.
Back to the scope discussion.
Optically, a scope should be clear edge to edge regardless of magnification.
We hope that as magnification increases, the scope retains its brightness and resolution.
I won't include tracking because that's not what you're asking about.
Most scopes including cheap ones retain their clarity in the center section. The center is where most aiming is done.
In a cheap scope, resolution decreases as magnification increases. It might not seem that way because the image is bigger to you but it's true.
Brightness decreases as magnification increases.
As a person ages, the clarity, resolution and brightness of their own eyes decreases.
My three step kids all have 20-20 vision. None have better.
Because their eyes are younger and clearer, they can see things with less light than I need. They can read in a dimly lit room just like I could when I was younger. Can I do that now? Not a chance.
I need light, I need brightness to make out details that were once a non-issue. Hell, figuring out the settings on the washer and dryer require my glasses and overhead lighting. Believe it or not, the back lit dial screws with my ability to see properly.
How does all this translate to useable and unusable magnification?
Not everyone's vision is the same. Scopes look different to different people.
As we age, magnification clarity and resolution in a scope become more and more important.
Can I still kill animals with that old 3-9x40 Tasco world class? Sure.
Can I find that animal in dense brush or thick grass. Not anymore. I need better resolution.
Can I still shoot groups at 100 yards with it? (Notice I didn't mention groups at 200)
Sure, but I can no longer make out the target as well.
Did the scope change? No, my vision did.
You're asking yourself where the hell are you going with this.
If you are just shooting groups in broad daylight, even at 600yds, a 20yr old burris 6-24 will still get the job done, even for older eyes. I know, I do it all the time.
If you are trying to use your scope to quickly find something before engaging, color, clarity, brightness and especially resolution absolutely matter.
Time matters and if you can't make out your target, you're losing precious shooting time.
I don't own any top tier glass. I also don't shoot PRS.
I do however understand why people buy the best.
Remember though, there are a bunch of people that buy and sell constantly because they don't have the latest, greatest. From them you can save a bundle buying their "last year's model".