MFU on BA is to WT+ and not to Club, so not really worth doing unless you expect to also get an op-up. You could go SCL-EZE-JFK-YVR (but no chance of op-up for JFK-YVR on CX). Tickets ex-SCL are rather expensive so I'm not surprised that the LONE4 is a similar cost. But I think you are deluding yourself in thinking that this LONE4 is pretty similar to DONE3 ex-NRT.