Shitloads of money. Massive institutional knowledge of public relations and marketing. Direct lines to Sony and Microsoft. Every kind of benefit of economy of scale you could want.
It's not like the idea of a barrier to entry is a new concept.
It's pure meritocracy here, if you are good then getting a publishing deal is not a problem.
The core of an "AAA studio" is a big fat wallet. It's essentially definitional. You're not actually saying anything with respect to them in any of your posts.
AAA do get a lot of money but it's the effect of them making games that sell well. There are dozens of startups in SF that cannot make even mobile games with their piles of cash and hundreds people. Money do not make you a AAA studio.