AA: SEA-SAP $395 ai
7180 EQMs on the SEA-MIA-SAP-MIA-SEA routing. More miles (8300) if you want to add AS (SEA-LAX-SEA) for around another $50 or so. Fall dates. First/Business class fares for ~$980.
Appears to require an overnight in SAP unless you can make the 1:20 hour turn at SAP. Maybe could be done?