Banksy Does Marketing.
Becoming the most noticed artist amongst the hundreds of thousand vying for that tag is a classic differentiation problem. You have to ensure you have a remarkable product and be really clever in your use of a combination of discovery and free to create a story surrounding it. The story generates interest in what you're doing and you start to reap the financial benefits because of it.
Some accuse you of daylight robbery, but you don't rest on your laurels. You continue to build the story by creating an astonishing event in a London road tunnel with very polite security.
In classic 2.0 style, you invite the public to view for free.
And others to collaborate and co-create.
Then, after three days, you will leave it to its fate.
And let the story and your popularity grow - while people reading this realise they have only two days to avoid the social embarrasment of missing it.