Depends on distance... A 400 mile trip will take a lot of time, food, etc.
While the 80km average per day equates to $10 per day.... But what are you saving (other than money) VIA bike? Consider current and future health - I know that's hard as it's not exactly tangible... It takes me, at a mostly recreational pace, 20 minutes to go 5 miles... 20 minutes a day of physical activity is the general consensus for getting a significant drop in cardiac risk (around 33% for women IIRC). 60 minutes being best
So lets say that - despite your car usage, you always do at least 20 minutes of bike riding but transportation bike riding can substitute. If 20min = 5 miles... That's 35 miles per week.
That means, 35 miles (specifically 5 miles per day) of biking food fuel is already covered to maintain health every week.
Just something to consider