Article is paywalled, but the headline says billions (10^8) and a suitcase has hundred thousands (10^5), and therefore we might be talking of around 10^3 suitcases. I can see why a 4x increase in the number of trips might be operationally significant. They might even be doing a trial run of 5 suitcases to check if they can make that their usual mode of operation since it'd be a substantial cost reduction.

> They were offered "around $3,750" to fly suitcases containing around $500,000 each. Which is not a high percentage even for just a single suitcase.

Couriers aren't really the value-add part of the operation, so this makes sense to me. Nearly nobody gets paid as a % of the value they are handling. A legal operation could move this for an order of magnitude less so there is actually a hefty premium here.