Price gouging is definitely a thing when you have a captive consumer base or inelastic demand. How much are you willing to pay for a bottle of water in the desert?
Price gouging is only a thing when you have both inelastic demand and a monopoly (which is why patented products like prescription drugs can be price gouging).
If someone is charging $1M per bottle for water in the desert, then pretty quickly a dozen more water sellers are going to make tracks for the desert.
Well, knowing I'm going to the desert I'm going to bring water. Just like how I eat before going to the airport because of the prices. That doesn't map to prescription drug prices, but it does for most things. What you described is more arbitrage than price gouging.
