"During these low-light tests I also had the chance to work with both the conventional RAW file size, which yielded approximately 77MB files" http://www.bhphotovideo.com/explora/photography/hands-review...
Which seems odd as 36.3MP * 14bits / pixel ~= 63.5 MB though it does say it can save both raw a JPEG at the same time which may make up the difference. That or it's saving 17 bits / pixel.
77MB * 5pictures a second = 23GB / min.
But, IMO your looking at it the wrong way as your not their target market. This is for HD video not camera's.
Still, the goal is not to fill the tings to capacity it's a cost / benefit trade-off is 500$ (800$ - 300$ for a 256 GB SD card) worth being able to take more than 256GB worth of pictures. And in that case it might be worth it simply to reduce the risk of missing a great shot. Even if they rarely want to go though 3,000 pictures looking for the best ones. There is utility in basically never running out of space. Plus a few applications where you might actually fill a 256GB card.
Of course, whether having an entire photoshoot on a single piece of (relatively fragile) storage is a good idea is another question entirely.