Best Buy has the Samsung PRO 64GB microSDXC memory card [bestbuy.com], model MB-MG64DA/BBY, for $23.99 with free shipping or free pickup in limited locations. Includes full size SD adapter.

This is gray/white PRO card that came out in 2014, not the 2015 black/white PRO+ card which cost $50 for the same size [bestbuy.com]. It is on clearance and "expected to get it by 7/25" for me so I suspect they're low in quantity.

This 2014 PRO (MB-MG64DA) card is rated at 90/50 MB/s read/write. As compared to:

80/20 for EVO+ and EVO Select series ($25 regular, $16~20 or lower when on sale)
90/80 for the 2015 revised PRO (MB-MG64EA, U3 rated, $30 at Amazon [amazon.com])
95/90 for the PRO+ series (MB-MD64DA, $50 at BB)

Note: a number of Amazon customer reviews state that the PRO cards (MB-MG64DA/AM) they bought in 2014 got close to 80MB/s write [amazon.com] despite the conservative 50MB/s rating. A number of Amazon customers who bought the 2015 PRO cards (MB-MG64EA/AM, U3 rated) said they received cards labelled MB-MG64DA but still perform near 90/80 [amazon.com]. So there's a good chance you'll get a PRO card with 80MB/s write.

Not bad for a MLC NAND card with fast (but not the fastest) performance. For devices that don't support SDXC, the 32GB PRO card [bestbuy.com] is also available for $16 but it's less of a deal -- Amazon currently has it for $17 [amazon.com], and the 32GB PRO+ card [bestbuy.com] is $25.