On a BDA-BOS(overnight)-RDU(stopover)-x/BOS-BDA trip I had a change of plans and needed to be in EWR before I hit RDU. Change fee was $150, but I found a $90 one-way ticket RDU-CVG-EWR that was valid only for a flight that happened to leave 45 minutes after I was supposed to arrive in RDU in the first place.
So saved $60 flying BOS-RDU-CVG-EWR instead of BOS-EWR.
Did I mention this was all on regional jets?