A lot of times items go through and I thought it was $35.00 canadian before they start charging duty and taxes. I have had items for a lot more than that pass through Customs with no problem. I always wondered why but didn't complain.
Its not usually that much depending on the price of the item you purchased and expect this if you are planning on buying from the US. There is an automatic processing charge of $5.00 though if they do decide to do the paperwork. And this might have went up some as I don't buy much anymore.