It is rather inappropriate to measure the monetary value of culture. Unless you sell a piece of art at the auction or run an opera theater, items of culture will hardly make a person rich. At least, so believe the parents who are afraid of their children taking more interest in drama classes than in math. But in fact, leisure industries make profit for artists and actors working within even though they shall work super hard to declare their talent.
Funding arts is as important as funding education or exploration of space. Large museums, exhibition centers, theaters, and concert halls are always packed with the public, which indicates that people seek emotional development. Art brings education, recreation, and spiritual elevation at the same time, which makes it so appealing. If we had no places to enjoy art, our life would be dull, monotonous, and too much down-to-earth.
As culture is no industry, it does not bring the immediate revenue. But can we imagine the government stop funding education or research that do not make a huge profit either? Perhaps, it is even more important to fund these spheres, because they work to the intangible benefit. It takes some time till theaters become super popular or medical research is implemented in the production of new drugs. In the world of free markets, we need to rescue such treasures with a subjective primary value.