I once found a first/business class ticket to Oslo from Ottawa that was less expensive than economy. Since I was travelling for work, I immediately took a screen capture, then booked the flight.
After the flight was booked and confirmed, I called Air Canada to ask why.
I was flying alone and my date corresponded with the end of the summer holiday. The airline was trying to keep dual seats open for families flying home so they were giving the reduced rate for singles.
I then tried booking for two people Just to see the price. The first/business class was back to its extraordinary price.
It was a fabulous flight.
I don't know if all airlines do that, but I'd recommend watching the flight prices at the beginning and end of Summer vacation. (If you are flying solo)
Also cleaning up your cookies in your browser and or using a different IP address might help. I saw a report on TV some time ago about the online ticket service website for our national airlines KLM. And they said that if they can track you successfully and you look for tickets in a specific narrow time frame, so they get the impression that the date you're gonna fly on is more or less fixed/you can't deviate from much and look for cheaper flights at other dates, they might use that against you and keep the ticket price higher because they don't have to compete with cheaper flights at different dates. If they are confident you are gonna buy a ticket they try to maximize profits. They also said the prices fluctuated throughout the day. At certain times when more business costumers bought tickets, prices were higher then in the evening when more private costumer sales are done.