Concur, the best methods to ship to Canada that I as a customer have appreciated is USPS (United States Postal Service (not UPS). Although not the fastest service, it gets here and its cost effective. As a past vendor of IT equipment (VAR), I preferred to use FEDEX AIR to Canada (lowest cost option - unless customer wanted it fast). The reason being is that FEDEX does all the customs work and collected GST upon delivery of the package and I didn't have to worry about it. The reason I was able to use FEDEX AIR at reasonable rates is due to the company I was representing. They had great volume discounts with FEDEX. If MASSDROP has a good volume discount with a carrier, then our shipping prices should be reasonable. The only reason for MASSDROP to use DHL, IMHO is for shipping outside NA (North America). UPS also is a ripoff artist when it comes to costs to Canada.
Alternatively there is FEDEX Ground for a cheap option, but the key here is to ensure that FEDEX is handling customs, they may be doing this now but not sure.