Unfortunately, this is the way things are. Not sure of the fancy term that AA uses, but some call it "Married Segment Availability." If you need to go from Tulsa to Austin, you would do a search TUL-AUS and get a price - say $100. If you were to then search for the TUL-DFW and DFW-AUS segments individually, it's highly unlikely you'd find that those segments were $50 each. Fares and availability are market specific. Previously, award space was not subject to these same controls and awards could be pieced together in the manner you describe. Nowadays however, award tickets (on AA metal at least) are based on the origin and destination. In this case, they are not willing to sell EZE-MIA-ORD-JAC for the Saver mileage level.