Best Buy offers the SanDisk Extreme HD Video 16GB Class 10 Secure Digital Card, model no. SDSDRX3-016G-A21, for $29.99. With free shipping, that's $1.87/GB and the lowest total price we could find by $9, outside of the below offer. (For further comparison, we saw a 2-pack of this card bundled with a case for $55 last week, since expired.) Sales tax is added where applicable.

Want to avoid tax and don't mind waiting? Amazon has it for the same price with an estimated ship date of one to two months.