I recently purchased a number of cards off Ebay and elsewhere that I had shipped to COMC. In case you didn't know, COMC offers a mailbox service where you can have cards shipped there and they will receive them and them to your portfolio for a fee. You can either resell them on COMC, or ship them to you.
Even with the additional shipping to my house, using the COMC mailbox service frequently ends up being a cheaper option for shipping cards bought in the US. The cost of shipping between the US and Canada is so expensive that packaging a bunch of shipments together with COMC and shipping them as one bundle ends up being the better option.
That is, until lately.