You can turnaround an A319 in ten minutes quite easily on a standard day. The next flight plan can be stored in a secondary plan and activated after landing. Panel scans take a couple of minutes including jotting down the ATIS, performance calcs are usually straight forward and the briefing can be done in less than 5 minutes if both pilots are familiar with the routing. What slows down aircraft turnarounds is getting the fuel, bags, catering and passengers on. We're usually twiddling our thumbs waiting for everyone else to catch up. Short haul is busy busy busy and learning to manage your time is one of the first skills you need to acquire.