Just so you know, if YOU as a person do not require more than one Safari tab then this does NOT entitle you to say that 1GB of ram is technically sufficient for the iPhone as a product. Just because you do not work at a level of productivity which requires multiple tabs to be open doesn't mean that other people do not or would not benefit from it.
This might come off as insulting, but it's just the truth:
If your work and school requirements on a phone aren't as demanding as others, then it's totally fine that you need a technically inferior device to handle your relaxed and less demanding work load.
But for us engineers, programmers, researchers, university students, marketing analysts, etc, etc... For people who have the capability, work efficiency and higher performance as professionals, Safari refreshing on one tab is a significant disadvantage.
But hey, if you're on Easy Street and coloring shapes for a living and doing one Google search per assignment, congratulations, you deserve a one tab browser. Might as well not even have a browser with multiple tabs. If anything, having the + sign is a disadvantage for you since it's so pointless.
And no, there is NO physical or quantifiable reduction in performance from jumping to 2GB DDR3L. If anything, the jump would create better battery life from a lack of page-file overwrites and usage of the onboard storage for temporary memory. It would reduce load on the CPU and flash storage and thereby reduce system load, thereby increasing battery efficiency.
From a cost perspective, it's peanuts. The CPU alone is roughly 25 to 30 cents to manufacture. Apple probably pays, at most, $150-200 per device (trust me, a LOT of the money goes to marketing and non technical divisions of Apple). The jump to 2GB, at most, would cost less than $5 per device, if that and that's a drastic overestimation.
The real reason they haven't jumped to 2GB is the same reason they haven't jumped from 16GB. Let me ask you this:
If storage jumps are so expensive, why is the 64GB iPhone 5S only $50 cheaper than the iPhone 6 64GB, yet in 16GB variations the price difference is $100? The reason is because if they bump the 16GB basic to 32GB, no one will pay an extra $100. There are people who pay to jump because 16GB is atrociously small and they figure, "Well if I'm going to pay extra, might as well get 64GB (Now 128GB)". But because 32GB is just right, they won't do it. And they get away with it because YOU apologists for Apple (who honestly have NO benefit for being such blind loyal fans, it's kind of ignorant really) defend this decision.
Your complacency is the reason 32GB disappeared from their storage options. They will NOT put adequate storage on the basic iPhone because they need to justify the $100 price hike, which is pretty much highway robbery.