As others have spoken about, if you're buying genuine Canon products, DON'T buy from a non-authorized dealer. This includes third party sellers with Amazon, even if they're "fulfilled by" Amazon, it doesn't mean they're genuine at all.
I also agree that third party batteries and grips are the only aftermarket items I feel good about purchasing. Canon's prices on these two type of items are INSANE. Instead of one Canon battery, I can buy two or three aftermarket chipped batteries and still put some money back into my pocket.