Amazon offers Prime members the Samsung 64GB Evo UHS-I Class 10 microSDXC Card with Adapter, model no. MB-MP64DA/AM, for $17.99 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $8.) That's the lowest total price we could find by $4, although we saw it for a buck less last month. It features data transfer speeds of up to 48MB/s.