Exactly.

I don't need to scam to make a profit, because unlike the OP, I'm not in a hurry.

I can take the 16.8 BTC that I purchase for $470.40 and list them on MtGox for $30/BTC.
When they sell I get $504 for them.

$504 - $470.40 = $33.60 profit for me.

Why would I try to scam $7 by not paying, when I can easily make $33 by being honest.

There is no financial incentive for me to scam with this deal, and every incentive for me to keep making the promised payments.