DL: SJC-SJU from $279 ai (9,146 MQM, 3.05 cpm)
Searchable on Google Flights
Overnight turns available (i.e. Fri Sept 25-Sat Sept 26)
Departures found between September 15-29
The lowest MQM cpm I can find on a quick search is SJC-LAX-JFK-SJU-JFK-LAX-SJC for 9,146 MQMs (3.05 cpm)
On DL medal. Books DL stock, V fares