Amazon offers its Prime members the PNY 64GB UHS-I Class 10 microSDXC Memory Card, model no. P-SDUX64U360G-GE, for $19.99 with free shipping. (Non-members can spend $49 or more to qualify for free shipping; otherwise, it costs an extra $8.) That's the lowest total price we could find by $4. It features write speeds of up to 60MB/s.