It can "move 100 petabytes of data in as little as a few weeks, plus transport time. That same transfer could take more than 20 years to accomplish over a direct connect line with a 1Gbps connection."

Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway. —Tanenbaum, Andrew S. (1989). Computer Networks. New Jersey: Prentice-Hall. p. 57. ISBN 0-13-166836-6.

I would propose making your postcard out of a 9x9 grid of 1TB microSDs and tape to give you an 81TB postcard that can be delivered overnight at the minimum price while providing 11.25 Gbps given the numbers you used.

But amazing to think how far technology has advanced.