I would not be surprosed if travel agents (either on line or brick & mortar) buy blocks of seats, rooms, etc. to resell including as parts of agency specific travel and tour packages.. The airline or hotel gets advance nonrefundable revenue in exchange for a bargain price for the agency. The agency price might not be less than the airline's lowest price at IPO but might use up all of the seats in the lowest bucket for a given flight.

From various complaints on forums such as Flyertalk I conjectured that airline schedule changes resulted in passengers try to reselect flights and travel agencies arguing about rebooking to a flight that also had a block of seats bought with some remaining versus having to go outside the box and book what the customer had as his real second choice leaving the agency with a block seat coming back and having to be re-resold.