I remember an article stating that embedded flash controllers typically have a 20MB/s speed limit. This in turn meant that wireless speeds beyond 200Mb/s were mostly worthless, because the devices simply could not utilise any more. If someone can find the article again, I would be delighted.
However: if the reality with RRAM is even half as good as the claims go, then it would certainly encourage the hardware vendors to invest in somewhat better controllers. After all, what good is a new, hyperspeed storage medium if you can't access it any faster than the old one?
The whole premise of taking NAND from 25nm to 19nm (for instance) is to fit more floating gates in the same area. You can take that as a smaller die, or as more bits on a slightly larger die than the previous generation.
Die size is indeed a major factor on cost. For a given technology (litho node + process, e.g. # and type of steps), the cost to process a wafer is fairly constant regardless of die size.
If you shrink a die size, you fit more die on a wafer. Additionally, yield goes up (given an independent manufacturing defect density), and especially for large die, the tessellation around the edges has a major impact.
Indirectly, even testing is related to die size, in that there is a limit to tester parallelism, and more gates means more time and more combinatorial patterns to test, e.g. for stuck-at testing.
There are of course non-linear costs in packaging and package-level testing and elsewhere.
[1] Which dominate with memory since production runs tend to be large and the regular patterns make for less design investment than, say, a CPU.
"[Crossbar's CEO] could not estimate the price of a 1TB RRAM module, but said it will cheaper than NAND flash partly because RRAM is less expensive to manufacture."
http://www.pcworld.com/article/2045926/startup-crossbar-pits...