Ask HN: 512GB flash is cheap and small. Why does high-end phones have 64GB?

I'm guessing power constraints. More flash you have, more power you'll require. Even increasing power consumption deltas minimally may impact battery longevity between charges on mobile devices enough to make it unfeasible with current battery tech.

"Power is an important consideration because the design of flash memories is closely tied to the power budget within which they are allowed to operate." http://cseweb.ucsd.edu/users/swanson/papers/TransOnCAD2013.p...

Device makers care more about capacity when thinking about which storage to use. Other things they consider include: power consumption, latency, bandwidth. It's likely that higher capacity flash isn't quite there yet.

What fraction of the market will use over 64GB? I'm guessing it is only a tiny fraction.

Ignoring that, let's assume there is a significant market there. What fraction of that market would be able to move their data from their old phone to their new phone? Again, I would guess a tiny fraction. Syncing 512GB in a reasonable time frame would likely require a direct computer connection at USB 3 speed or thereabouts.

So, your best bet likely is a phone that allows plugging in a 512 GB flash module.