Customs Duties
 

I just bought something online on eBay and the seller is willing to put a lower customs value on it. What kind of fees would I be looking at customs/duties/taxes? How much are the customs/duties fees usually? Do I have to pay GST and PST for the item too?

The item was just above $500USD including shipping. What price should I tell the seller to declare the item as before he ships it out tomorrow?

BTW it's shipping from the US.

Thanks!