The 1911, not the AR15.
Parts are parts - but with the 1911 they have to be fitted, which means they won't likely fit another 1911 straight across. You can do that with the AR15, it usually requires no change at all. If anything the AR15 is the antithesis of the 1911, it rarely if ever needs hand fitting. It truly does go together with parts from opposite ends of the country and diverse makers.
You try that with the 1911, and nothing works right. It takes skilled, knowledgeable, experienced hand fitting, because the 1911 was designed and is still built with such poor standards in blueprinting that almost NONE of the critical parts work right the first time.
Think, pre 64 Winchester. Yeah, the one that nearly drove them into bankruptcy.
For every part you buy for a 1911 you also have serious expense in labor to install it. Not the AR15, and that is where most are wrong about it. Nobody has to spend $150 with gunsmith to install a new trigger in an AR. If you can do that and get exactly the pull you wanted with the 1911 then your burnt offerings on the altar of your local gun range just may have been acceptable.
I suspect you could assemble half a dozen working AR's in the time it takes to just check what is needed to be done to get a pile of 1911 parts working. And every operation on the 1911 requires finessing the fit in measurements of thousandths.
I won't even begin to compare the finishing of an 80% lower. That's another exponential step up in costs. And the cost of acquisition of those parts is another hurdle - barrels seem to be running slightly lower on the low end, otherwise, head to head, and it would be really nice to buy a forged aluminum 1911 lower for $50, wouldn't it?
Think about that. 1911 frames aren't that much harder to forge and machine in quantity. I don't see AR frames being machined in halves and brazed together. I also don't see a lot of AR's being imported from Turkey or the Phillipines with Colt markings, yet we get 1911's rollmarked in factories for major name Brands who tout superlative excellence.
Nope, AR's aren't huge money pits, it's the 1911 and how the industry has jacked up buyer standards to the point that only a tightly fitted competition grade pistol that can't operate consistently in third world conditions is appreciated. 1911's are the Escalade of 4WD today, they share the main feature and size, but the majority of the expensive ones can't really do the job nor would anyone even attempt it. Yet their fans are incapable of admitting it. AR's aren't the money pit when 1911's at twice the price sell because the public lines up to buy the sizzle, not the steak.
Can you buy an AR manufactured from meteorite? You can a 1911. A dual action AR side by side? You can a 1911.
The 1911 was a huge money pit long before the AR and continues to lead the pack. Some of the first mods to AR's were adding 1911 grips. At least that didn't take a gunsmith to do it.