Provocative. I'm not sure I agree, as certain directors have funded their own work entirely themselves. Apocalypse Now, for instance. That's an example of a very expensive film made by a director who got rich initially working within the system (with The Godfather films), but I do think whether expensive or cheap, if the film itself exists without interference, made without compromise by the artists concerned, it is a work of art. Distribution is irrelevant, because even without that, the work of art exists. Therefore cinema can be art, by your definition, if the project is entirely self-funded.

Of course, I'd argue it can be art outside of your definition too. :)