OP wants to buy a RT ticket, which presumably has many restrictions, because it costs less than a OW ticket. A flexible fare would almost certainly be significantly more expensive than OP wants to pay in this instance. Technically there's no penalty for not showing up for the return flight, but I would recommend OP cancel the return flight after s/he has taken the outbound flight. There's no penalty for cancellation other than losing the value of the return flight. AA would then be able to sell the seat, happily, to someone else.