Amazon offers Prime members the Transcend 16GB microSDHC Class 10 Secure Digital High-Capacity Card with Adapter 2-Pack (pictured), model no. TS16GUSDU1X2E, for $19.99 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise shipping costs $8.03.) That's $0.62/GB and the lowest total price we could find for this quantity by $7.

Also available is the Transcend 32GB microSDHC Class 10 Secure Digital High-Capacity Card with Adapter 2-Pack, model no. TS32GUSDU1X2E, for $37.99 with free shipping. That's $0.59/GB and another price low for a 2-pack by $4.