You seem to be missing the way the website currently works- at least for most of the fares. The OW fares you see are "OW based on RT purchase," as it says there. If you actually try to purchase OW, you will likely not see the same fares.
Cheers.
I'm with tkelvin69.
There's a lot of fares I see on AA.com which are priced identically for OW as well as RT.