Walmart offers the Samsung 64GB EVO UHS-I Class 10 microSDXC Card with Adapter, model no. MB-MP64DAT/WMT, for $23.99. Opt for in-store pickup to avoid the $4.97 shipping charge. That's the lowest price we could find by a buck, although we saw it for $1 less last month.
Update: Amazon offers it for the same price for Prime members.