You can now buy 128gb USB sticks or SD cards for around $20. Meanwhile, 16 gb RAM sticks still are $100+.
Are the performance specifications for RAM that much more stringent? Is the demand for SD cards and USB sticks that much greater that there's more economies of scale?
MLC is half as expensive as SLC. TLC is 33% less expensive than MLC. QLC is 25% less expensive than TLC and 75% cheaper than SLC. Not to mention transparent compression algos. As the controllers improve you can get more bits of storage from the same amount of flash for free. Longevity and reliability suffers, but hey, cheap SSDs!
Ram only gets cheaper by improvements to semiconductor processes, which also can be applied to make flash cheaper. (Big fat asterisk, those processes are very different.) While improvements to flash that allow more levels per cell can't be applied to ram. The price difference between flash and ram will only continue to grow.
Modern flash is quite "analog". The first company to figure out how to reliably store 32 voltage levels per cell (Five bits. PLC?) will make a quick billion.