MicroSD cards come in a variety of sizes, but the largest ones give us something to aim for. They're aspirational. No, I'm not going to spend $400 on one when it first comes out, but I know that someday, eventually, I too will be able to afford nice things. And sure enough, the price comes down. Then it drops again. And again. And againRight now SanDisk's 200GB microSD has lowered to $135 on Amazon.

I hear you—that's still a lot of money. That's phone money. You can buy a Moto E and stick a 64GB card in it for that price. But on the other hand, sticking a 200GB microSD card in an Alcatel OneTouch Idol 3 is going to cost significantly less than a 128GB Nexus 6P. If you really want to treat your phone as a portable hard drive, the cost of this microSD card is steadily entering the range where buying one makes sense.