GoToGate offers a number of airline tickets and deals. What they don't tell you is if a particular airline has additional taxes. When flying from Harare to Johannesburg, I selected the cheapest flight on offer on their website, one with Air Zimbabwe. What they don't tell you is that Air Zimbabwe passengers pay an additional US$50 at the airport, unlike passengers on any other airline. Had I known this, I would have booked with the next cheapest airline, the ticket for which was only US$20 more expensive than the ticket offered by Air Zimbabwe which would have saved me US$30 overall.
It is a great way to ensure you get tickets sold on your website!