It's called arbitrage.
Eventually, other people figured it out and the prices leveled out.
Arbitrage opportunities crop up all the time.
[1] https://www.youtube.com/watch?v=bNBy1D1Y0h4 damn I was only familiar with the audio; this aged extremely poorly.
[2] https://en.wikipedia.org/wiki/Ward_Cunningham#Cunningham's_L...
https://www.smh.com.au/technology/adobe-chief-dodges-questio...
Here's the kicker: the tripod and head were both produced in Italy. So it was somehow cheaper to ship them halfway around the world and pay import duties twice than to buy locally with no import duty (since it's the EU).