Repricing to lowest economy this close to departure gotta be crazy high too right?

It's selling at Y (class) one-way but I don't know how repricing works on a return segment. Can i get the lowest economy fare class available (say K) or do i have to get the lowest fare available? If the latter, is the fare based on one-way in Y class?

i was hoping maybe a R basis can be rebooked into B without add collect