There is no "cheap" method. The least expensive has always been USPS BUT I would go so far as to say there is not a single business in the US who will ship to you that way. So you're stuck with UPS, FedEx, etc.. USPS shipments quite often would come in without being taxed HOWEVER, the courier companies will squeeze you for every cent AND charge brokerage fees on top of it all. The brokerage fees never show up on an online quote - they like to surprise you at time of delivery!
Brokerage is a MINIMUM of $35 US.

Depending what you need, try the guys at National Moparts in Ontario.