This all makes sense. Thank you to all for the info. This was a rush of a flight for family member (emergency itin and booked it 3 hours before departure and then packed in a hurry), and wasn't about to start ripping open bags and trying to free up weight with minutes to spare at the check-in desk. I recognize they were overweight and was happy to pay for that -- the agent explained that the issue with the bags was strictly their weight. No mention of oversize although I guess based on the rough math from posters above, that is probably where they are coming from. I have one long bag and one pretty standard size suitcase -- if the clerk isn't mentioning "oversize," asking you bag dimensions, or measuring anything, are they just eyeballing the bags and choosing to apply the fee? Again, what was relayed to me was "your bags are too heavy, look at the scale, it's going to be $600 if you want to check them at this weight." She also made me come around the counter and hoist the 85 lb bag onto the conveyor belt , so I left under the impression everything was related to the weight.