It is beyond my comprehension why Travel Agencies could do this to bring the price ticket lower. How was it made possible?

70% of the flight ticket on the planes are sold through travel agency. This works specially for the major airlines like United Airlines, Delta Airlines, American Airlines etc. The Airlines have a separate desk call travel agency helpdesk, which controls the travel agencies from the back office. The Airlines sell their ticket in bulk to the agencies and suppliers. It is generally called unpublished rate, or in the airline’s jargon “Net Fares”. There are other types of ticket called “Bulk Ticket” which is available only with the travel agency. These are relatively lower cost than the ones that we can get in the airlines website or from the airline’s reservation office. These types of ticket have their pros and cons, being cheaper in price is the ultimate goals. Its setback are felt if we want to change the flight date, timing or if flight has to be cancelled due to voluntary decision. The bulk ticket comes with a lot of restrictions and it is hard or expensive to make changes. However, there is a good news. If you have purchased these type of fares, and if you are not sure of any change in plan due to several reasons. Apply for insurance, which will cost around 10-15% of the ticket cost. The insurance company will cover the loss incurred under the circumstances that you satisfy their requirement and policy. 

Happy traveling folks!