SD cards are everywhere now, and you can get them on the cheap. But SanDisk is not interesting "on the cheap" with the announcement of some crazy, insanely high-capacity flash memory that is more expensive than the camera you put it in.
The new SanDisk 512GB Class 10 ExtremePRO SDXC card retails for $800 and holds a veritable buttload of data. Like, you can shoot your whole day in burst mode. It's touted (by SanDisk) as the highest-capacity card in the world.
All jokes aside, SanDisk mainly has 4K video in mind with these new cards. Ultra high resolution 4K files tend to be huge, and video shooters need a lottttt of card space to store them. It is interesting to note, however, that most cameras that shoot 4K and record to SD cards use highly compressed files, which aren't huge in size, and probably don't require amounts of space that are quite this extreme. The new cards have a read speed of 95 MB/s, and a write speed of 90 MB/s. That should be enough for most 4K video sources.