Ah. This old argument again. It would make sense if people actually support artists. Every time some one brings this up in real life, I ask them for instances where they have actually supported somebody.
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.
Nine Inch Nails? Seriously? I'm pretty sure they had already found success through the traditional channels before they had the ability to do something like that.
Crowd funding works in certain contexts, but it's no magic bullet.
Don't get me wrong. I like the crowd funding model, but the real world is not so perfect. We should not say "I won't pay for this, since somebody has already paid for it. " That puts everyone in a bad situation.
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.
Commissions are the same as Kickstarter, IE you pay before it's created. In no way does something like this have any bearing on works by commission, in fact it puts things back on the path of human traditions, which have typically relied on commissions, patronage or performance, rather than ownership.
And I bet most people can give you several. Can't remember the last time I bought a DVD or vinyl record, without having enjoyed it somewhere else first, for free.