Maybe, if they're buying the memory at market prices. I believe that for high-volume NAND flash consumers, there is probably more of a spot-pricing scheme in place: for whatever reason, if Micron had a whole bunch of 64Gbit MLC around because (say) HTC stopped making a phone yesterday, then Transcend would be plenty happy to scoop it up for a low price.
(edit: Googling for NAND flash spot pricing results in http://www.dramexchange.com , which seems to confirm those sorts of suspicions. I think the market is probably pretty volatile...)
SD cards are the lowest bin tier as well, given their low performance requirements and low margins relative to SSDs, embedded designs, etc. The leftovers and rejects tend to end up in that channel.
In that vein, the 64Gbit micron devices may in fact be 128Gbit die with half dead arrays -- so they may have a similar process node and reliability to the samsung device.
(edit: Googling for NAND flash spot pricing results in http://www.dramexchange.com , which seems to confirm those sorts of suspicions. I think the market is probably pretty volatile...)