Yes, Apple has tons of cash. However, it can't necessarily hire however many engineers it needs to add a feature in for product year X -- it may take those engineers months to get up to speed, and more staff doesn't always equal better. That and Apple has run a lean outfit ever since Jobs' return. It tries to avoid taking on engineers that don't have much to do.
That is the exact opposite of what I have heard about the modern Apple. On one podcast I listened to Harry McCracken (Fast Company) blatantly said that Apple hires hundreds of engineers just to work on different POSSIBLE product categories (like VR or cars) and only if it looks like something will work out do they expand into having thousands of engineers work on it.
Even outside of those claims, you figure they spent BILLIONS on R&D for the Apple Watch while someone like HTC can create and ship the Vive on a shoestring budget. I refuse to give Apple the underdog advantage, they have the money to make their most success product (THE most successful product ever) as good as it can be. There is a manhour problem (aka 30 engineers can't do something 30 times as fast as a single one always), but Apple has the resources to refresh the damn phone every year if they wanted to (or more exactly if they needed to).
This isn't to say that this is a definitive answer, but to paraphrase: never attribute to conspiracy what can be explained by sound logic. It's easy to claim Apple is holding back on certain features without knowing about the design and engineering battles that led to it being late/non-existent.
I get that. I also understand that even Apple can sometimes be too quick to push something to the detriment of customer (iPad 3 anyone?). It has to be a balance.
The iPhone 6/6 Plus' RAM I'm not sure about; you could be right, or it could have been due to power saving concerns in 2014-era tech.
I simply cannot accept that on the 6 Plus.
On the regular iPhone 6 I MAYBE buy the battery life thing, but the iPhone 6 Plus had a MASSIVE battery (bigger than the S model) plus the eventual iPad Air 4 showed us Apple could have bolted 2GB of RAM on an A8 all along.
There is no way to explain why they gimped their first phablet in such a way that doesn't show extreme profit seeking that any reasonable person could confuse with consumer malice. Combine that with the shitty flash memory many iPhone 6 Pluses have and you have the making of a ticking time bomb of a iPhone. I call foul on that, and I always will unless I see evidence that proves there was no way Apple could have done any better at any cost.