"How does it compare with FTPing a tape image? Or even the classic "747 full of DVDs (or Bluerays)"
The bandwidth of a 747 full of media is well in excess of 10TB/s  so the raw transmission time for 1GB is less than a millisecond. A motorcycle courier can manage 1GB/s (i.e. 10Gb/s) London to Edinburgh.
Ping time is several hours though!
I cannot remember a time in the past (nor envisage one in the future) when any networks had a higher bandwidth than the movement of contemporary physical media.
 A 747 can carry 100 tonnes of cargo (I think), a 2TB SSD weighs less than 100g including appropriate packaging, meaning that is 2 Exabytes per Jumbo, say 8 hours for a LON->NYC flight time and 2 more hours handling time, around 50TB/s unless my maths is letting me down.