I wonder how much of a market there is for people who already know how to do BGA soldering (i.e. many phone repair shops) to offer RAM upgrades at a fraction of that cost.
They aren't fungible, but even for a high-end 512GB SSD, $200 is rip-off pricing. In fact, a top-end SSD range won't even offer 512 sizes because aside from not really being worth it, transfer-rate performance is lower with smaller chips.