So basically, your statement didn't mean anything at all, hags. It was a comment, worded so it was not understandable as such, about some people you have encountered, without mentioning those people until now.
There are guns that are truly more than the sum of their parts. Generally, those are custom bolt guns or handmade muzzleloaders. Anyone can buy the parts, but only a few can turn them into something great.
The AR, on the other hand, is engineered to go together like a very precise puzzle. All the "more than the sum" is in the engineering and initial manufacture. Modular guns designed for mass production tend to be like that. If you take the parts of any 870 and put them together with others that are not damaged, the gun works perfectly. That's the point of the engineering.
One can screw up an AR, and turn it into something less than the sum of its parts, but all it requires to make it work as intended is proper assembly. That's not such a big deal, due to its design.
It sounded as if you were trying to tell someone that he has to be a skilled gunsmith or gunmaker to build a good AR, and that's just the usual BS I expect from a dealer who sells the things. Those of us who have spent some time on the other side of the counter, and have some knowledge and experience, have heard more BS from gun dealers than perhaps anyone else outside of car salesmen.
Pardon me if that's not where you're coming from, but, like you, I've had some experience with certain types, and the red flags go up.
Now, without resorting to something as vague as "more than the sum of its parts" which has no concrete meaning, can you tell us WHY a Colt is worth the premium price over another gun with quality parts and the same specs? (Note that the Army apparently doesn't think Colt is "all that", either.)