- not every cart has to be 64gb
- 64gb costs 3$ in bulk. Nintendo could make sure the cost for this is included in the license fee
- cartridges actually lower the cost of stocking shipping. There's a great post about this over here: http://www.neogaf.com/forum/showpost.php?p=192728798&postcount=557
That's just not true. Go and check on alibaba, I'm sure nintendo can get better quality/rates than me.
They can't just install a game on an SD card and call it day. There are other costs to consider as well, such as encryption and making it read-only (or only writable by the console in what you think will happen). That could easily double that, which is several times more expensive than a disc.