So, apparently Sandisk's 200GB microSDXC cards aren't really 200gB, and I'm not talking about 200GiB vs. 200"GB". They're only 196,865,949,696 bytes. I guess selling a 196GB card just didn't have the same cachet.
In contrast, Lexar's 200GB card is 200,788,672,512 bytes. I noticed the two were...