Shipping costs all depend on weight and volume. A minimum door to door cost is different when using air, express courier or seafreight. Before you can decide on the cheapest price, you have to have a value for the weight and volume.
Unilaterally, the very cheapest cost of shipping is postal services but..there are limitations on this.
If you do not want to go post, then courier is the next cheapest but only for under 25 Kgs (and remember that the volume of your pcs may generate a higher chargeable weight. ) Further information on chargeable weight can be found in the recent video/pdf at http://www.secondreview.ca/videos/airfreightpricing.html
The next cheapest is seafreight but again it comes back to weight/volume as seafreight minimums are very high on the total door to door costing.