I once sat next to a chap on KLM and discovered during conversation that I had paid one third what he paid for the same ticket.
I'm sure it wasn't the same ticket. Same ticketed cabin, but for that price differential it most certainly wouldn't have been the same type of ticket.
Some airlines do offer a rollback feature, like AA. If the price comes down after you buy, then they'll refund the difference.
In the industry it is far more common for prices to rise rather than fall, but at times a new promo fare will be introduced like this that undercuts the previous price. Also it is not always true that the closer to departure the more expensive the flight. Sometimes a few days before departure you can snag some great bargains as the airline struggles to fill seats. Nothing wrong with that surely?