So, you've got a massive library of media, and you absolutely must have as much of it with you as possible at all times? Sounds like you need a gigantic microSD card (and a phone that supports it, but that's a story for another day). But oh, the cost! Well, there's a sweet deal on a PNY card today at Amazon. 128GB for thirty-five smackers.
This card usually sells for around $50, which is about as cheap as all the comparable ones are. Some are even more than that. SanDisk's 128GB card is $50 right now and Samsung's is $55. $34.95 is a pretty good deal by comparison. The price has bounced around a bit lately, but this is the cheapest it has gotten.
The PNY card has Prime shipping, but be aware it doesn't appear to come with a full size SD adapter like many cards do.