You don't need me to tell you why expandable memory is nice. Sure, the user experience may not be as smooth as simply having more internal memory, but no amount of built-in storage will ever equate to a larger number than 64GB more.
And right now you can get that many additional gigabytes for just $18.74. That's how much Samsung's 64GB EVO MicroSD cards are currently selling for on Amazon.
Samsung's smaller sizes are also cheap. A 16GB card will only cost you $8.72, while the 32GB option is just $12.47. At $64.99 though, the 128GB card will still set you back quite a bit. You might want to go with SanDisk and save yourself a few bucks if you need that much space.
The card is now down to $17.57, still with Prime shipping.