It isn't SFO, but I'm seeing ORD-DUB for $321 all in. Looks like to get this you've got to fly DUB-BOS on Aer Lingus for the return. I hear tell that miles on Aer Lingus aren't EQM, but only RDM.

Add: I just found SFO-DUB rt at $359, though two of the legs are on Aer Lingus.