Ah this old misdirection. There is no shortage of evidence of voluntary payments for creative works so stop spreading bullshit. How far do you move the goalposts when people mention examples like the Humble Bundles, Nine Inch Nails, etc.?
Go on. You might be able to cite Radiohead's In Rainbows. Did these new distribution models flourish, or were they one-off experiments? NIN's new album is available online now for a fixed price.
Crowd funding works in certain contexts, but it's no magic bullet.
My policy: Enjoy something? Contribute back (or pay forward) in some tangible way.
There is also the aspect of risk. Do you pay someone before or after they make a product in an unknown market (E.g. Will this game be successful?). Paying for it rewards them for taking that risk.
Of course, if you commission something beforehand, you take away some of this risk, and the artist should gladly part with some of the rewards.