The season ticket only covering station-to-station travel means you're still left with covering the leg at either end. As an example, this is likely still going

The season ticket only covering station-to-station travel means you're still left with covering the leg at either end. As an example, this is likely still going involve a car journey plus parking costs at 'local' station, and a Tube trip to the office at the other end. I think any potential cost saving quickly disappears, while still being left paying for only a single route.