To get hit with customs is VERY random.
Businesses in the U.S. very seldom mark it as a gift and declare it for a low value because of insurance purposes. It's not so much about abiding byCanadian custom laws (they're American, what do they care?). Should the item ever get lost, they can only recover the amount they declared. And becausethey're a registered business, they can't mark things as "gifts" too often.
Pretty much, it's like this:
GIFT + high value = tax
Commercial item + low value = tax
It's very much to their discretion, is your package worth their time with paperwork? Are the nearing quota lows? Is there too much cross-border/ cybershopping?