RET, funny initials, I know, but just to introduce you all to a wee Scottish secret. Road Equivalency Tariff.
To explain. Subsidised by the Scottish Government in agreement with the UK government and the European Union, the ferry is meant to cost roughly similar for a vehicle as if it was a road with a nominal toll. By 2022 this is scheduled to be rolled across all ferries in Scotland. Slowly it is being rolled out across the country. This year I am planning a couple of nights on Arran thanks to RET which has seen the price drop by over 50%.
It started on the Western Isles routes, expanded to the inner Hebrides routes and has this year spread to the Clyde routes.
If planning, check to see if the route comes under RET. It may change from no to yes during your planning.