C + Y > D + D.
QED
Welcome to the surreal world of Airline fares.... What you might be bumping into could be combinability issue -- you asked UA to find you an economy ticket and it wasn't available -- so it got a full fair Y on the second second and looks to find a fare on the first segment that it can combine that with -- in your case a "C" -- and that makes for one expensive ticket....
Last edited by Textile; Oct 9, 20 at 9:08 pm