A 1 TB drive posted next-day moves data at an effective 93 Mbps, so it beats any connection slower than that. At 20 TB the courier is doing 1.9 Gbps.
Bandwidth and latency are different things, and physical shipping is the extreme case of the trade: appalling latency, enormous bandwidth. Because the effective rate scales with how much you put in the box and the transit time does not, the crossover arrives far sooner than people expect. Bulk data migrations are routinely done this way, which is why the large cloud providers all sell a service that is, in the end, a lorry.
It only holds for bulk. Anything you need soon, anything that has to arrive in a usable state as it streams, and anything small enough that the transfer finishes inside the postal delay all go over the wire. The comparison is throughput only — it ignores that a drive can be lost, damaged or read by whoever handles it.
Estimate with the rule, then check it against the calculator that models it properly.
Open Data Transfer Time Calculator →A 1 TB drive posted next-day moves data at an effective 93 Mbps, so it beats any connection slower than that. At 20 TB the courier is doing 1.9 Gbps. Bandwidth and latency are different things, and physical shipping is the extreme case of the trade: appalling latency, enormous bandwidth.