Adorama offers the SanDisk Extreme 64GB microSDXC Class 10 UHS-I Memory Card, model no. SDSDQXL-064G-A46A, for $41.95 with free shipping. (B&H Photo-Video charges pennies more.) That's $18 under our April mention and the lowest total in-stock price we could find by $11. It features read and write speeds up to 45MB/s and is water-, shock-, and X-ray resistant.
Need more than one? Add two to your cart to drop the price to $40.95 each, or three or more to cut it to $39.95 each.