Flying from IAH I often pay over $2500 for a two or three night TATL itinerary that can be purchased for $800 with a weekend stay. But at least I always meet the minimum fare class to use a GPU. I literally NEVER have to worry about that for TATL trips.

As for domestic RT vs OW, flying from IAH I often see the RT price $25 or so less than the sum of the two one way trips. It is definitely different on the routes I fly most often, but not such a huge difference that it’s immediately obvious when checking flight options.