> I think most people don't realize how slow SD cards are compared to conventional flash, too. When you put apps on a SD card on Android, it's always been dog slow. And you're at the mercy of the manufacturer to put a reasonably high-speed interface on it.
It's been a long, long time since I couldn't fit all the apps I wanted on the phone storage. My SD card is mainly for multimedia files, and it's plenty fast for that purpose.
The only performance limit I've hit in recent times was because it was exFAT, not because it was an SD card.
> There are options; NVMe and CFExpress cards exist. But they're large
Ignoring SD Express as a failure to launch, UHS SD cards can be plenty fast if they're designed to be. A hundred megabytes per second is not a significant bottleneck if individual IO operations are fast and it can do many of them.
Also there was that XFMEXPRESS form factor if manufacturers wanted to put an SSD socket into a phone. "card size is 18x14x1.4mm, slightly larger and thicker than a microSD card. It mounts into a latching socket that increases the footprint up to 22.2x17.75x2.2mm."
> and I doubt that people are going to pay that kind of money even when they currently pay it for onboard storage.
That's the real killer incentive, that you can charge huge amounts per terabyte and also force people to buy higher-end phones just to get the ability to buy more storage.
As opposed to the user spending $40 for a 512GB sandisk extreme, and giving the phone maker no extra money.