The first known example is the 6th century BC, where a greek philosopher cornered the market on olive oil presses, because he predicted a richt harvest via his knowledge of astronomy:

https://en.wikipedia.org/wiki/Cornering_the_market#Thales_of...

Tyson Foods, Cargill, JBS, and National Beef controls roughly 85% of the U.S. beef market

CVS Caremark, Express Scripts, and OptumRx manage over 80% of all prescriptions in the U.S

Amazon buys 50% of all books.

These examples are even more extreme than at least 3 major clouds present in the US buying hardware.