Zones 1-4 is the cheapest day ticket available, that’s why I took it as an example. Feel free to look into the provided links if you think there’s a better example listed.

I'm not debating that. London is over x2 the size of Hamburg. Towns that are in zone 4 are around 15km from the center of London, in zone 6 it's close to 30km. I live in London and commute everyday, I'm acutely aware of the cost of travel in the city.