I investigated why airport currency exchange booths put different prices on buying and selling.

On the electronic board of an airport currency exchange booth, the same 1 dollar has two prices attached. Expensive when you buy, cheap when you sell. Most people think this is the bank ripping them off, but if you dissect that gap piece by piece, you find layers stacked on top of each other: air transport costs and armed guards, the interest on money locked in vaults, inventory risk that fluctuates every second, and the liquidity tier of the currency. We follow how travel cards brought this cost down to zero, yet why they still charge a fee when you sell back, and how this small gap became a crisis alarm bell in 2008. At the end, we talk about how the standing of the Korean won — a mere 1.8 percent of global foreign exchange trading — comes back to us individuals as a cost. ⏱️ Timestamps 00:00 Introduction — Two prices you face in front of the board 03:20 Price gouging, or an inevitable cost? 06:17 The first stratum on the bedrock — The weight of banknotes as physical objects 09:01 Money locked in vaults and inventory that fluctuates every second 12:28 The biggest variable — The tier table called liquidity 15