From the above chart it looks like about 100,000 people commute via bus into London per day during the morning peak.
“At over two billion passenger journeys a year, usage is around double that of the London Underground. The city has 675 bus routes, with around 9,000 buses in operation and over 19,000 bus stops.”
From the above this is roughly 2 billion / 365/2 = 2.7 million trips per day, so it can be reasonably approximated to the number us users.
This means that each user is receiving roughly £222 per year in subsidy.