SteveM has pretty much summarized the issue-at-hand.

The OP's going to have a lot of 'splaining to do if he claims as $500 CAD and the Customs official finds them. A lot more than if he just claims over $10K.

That's equivalent of me buying a $30K gold watch and claiming it for $1K because I've got a receipt for $1K.

For me, I always take the most prudent course of action. Less hassles in the long-term.