https://www.utsource.net/itm/p/11213515.html
84cents each, but you'd need a buffer and a voltage regulator to step down from 5v to 3.3v
Perhaps the 74LVT162244 as the buffer?
Each chip is 8MB (64Mbit) in size, 8 chips needed for the full 64-bit data bus, which would also give you 64MB...