Booking flight for July

[KittenKong]

I checked the same flight on Qatar Airways site and it's 617 Euros, so not sure how Airtickets can do it at this price.

There is nothing very unusual about agents undercutting the airline's own website. I often buy my tickets via an agent (consolidator) because it works out cheaper. Also airlines often force you to pay in particular currencies whereas agents generally offer a choice, and that can be another saving depending on the exchange weighting of the card you use.