I got what I thought was a decent deal redeeming SkyMiles: for 58,200 miles I got an open jaw main cabin ticket CLE-DTW-LHR / CDG-DTW-CLE, plus $97 in taxes/fees (the cash price on this was over $800). I upgraded the eastbound TATL to PS for $400 cash (they want $780 for a westbound UG to PS, which seems silly).
Had I done a RT returning from LHR, the taxes/fees would have been $204.