http://www.cnet.com/news/sandisk-bea...it-isnt-cheap/

SanDisk beats rivals to 512GB SD card -- at a whopping $800

[...]

As SanDisk phrases it: "The new offering is designed to meet the demands of industry professionals who require the most advanced gear available for shooting 4K Ultra High Definition (3,840x2,160p) video, Full HD video (1,920x1,080) and high-speed burst mode photography."

As such, the card can deliver a high enough recording speed, designated as UHS Speed Class 3, to ensure high resolution, real-world color reproduction, and stutter-free 4K ultra HD video. SanDisk also promises transfer speeds as high as 95 megabytes per second to quickly move the data off the card to the computer for post-production work.