are people buying these to sell the tickets to others? how does one make money off this?
First of all, it’s not always about making money, it can also be about saving your own money. So you’re traveling somewhere on air Canada, If your ticket is around $1200 or more, it would make sense to buy a 15% off certificate for $150 or so. And now imagine if you’re taking a family of four on a long distance flight, where the fare could easily run a few thousand dollars, or substantially more if you are flying business class, which these certificates work on. And secondly, travel agents will sometimes buy these because they can provide a greater savings that they can get solely from being an agent.