Archive thread, active thread is
Consolidated "Why is this UA fare so expensive?" thread

Potential reasons for high fares
-- the lower fare classes are sold out
-- the lower fare classes are not available due to fare rule restrictions
..... day of the week travel restrictions, Saturday night stay requirement, minimum stay requirement, advance purchase requirements, ...
-- desired fares are not combinable
-- discount fares not available for one-ways, only roundtrips Why are international OWs so expensive, such high fare classes?
-- discount inventory for codeshare marketing airline is gone, but flight operator may have discount fare (or the reverse)
-- Plating -- airlines restrict the best fare to their ticket stock, meaning ticketing that flight on another ticket stock will be more expensive
-- Airline is figuring it will still sell (due to last minute purchases0 even if the competition is lower earlier. Such as peak leisure periods or special events.
-- Airline is placing a premium on non-stop (monopoly?) versus alternative connecting routings

If you find an expensive flight, start by checking the fare class and compare to the less expensive option -- that generally will explain a lot.