I have tried this. The phone managers say it is a corporate decision to streamline their shipping process and eliminate the time it takes for them to process the international shipping documents (five minutes...) etc. Bottom line is saves them a few dollars in wages and time, and offloads those and more costs onto the purchaser.
On large purchases, this makes sense. You are going to get a brokerage fee and manifest paperwork charges anyways, so no big deal. Duty will be assessed at the border. The main problem here are the brokerage companies that find a way to charge for "brokerage" plus a "document prep fee" on your package. No matter the size of the item, if it is expensive their charges reflect a portion of that cost. Almost like real estate commission. An example was my coil overs. $850 US for the coil overs. $125 US for shipping, $75 Cdn tax at the border, $200 Cdn brokerage and document fees! But yet somehow I manage to get 100 lbs of metal poles (wedding backdrop) shipped from China for $25 Cdn.... no brokerage, no fees, not even stopped for tax assessment.
I ordered a crimping tool for the EZ Clip A/C system. $49 US for the tool. $26 US for the shipping. I asked them why so much for shipping and they said it was because they don't want to bother with USPS shipping when they can offload to UPS or FEDEX. The result is a small letter sized package that would have cost $12 US to mail, cost me $35 Cdn to receive.
As much as I try and support my favourite vendors, it is increasingly more difficult to justify the expense. I order from Canadian companies whenever I can, and overseas for others that offer huge savings on shipping costs. I don't order Chinese junk, obviously, but sometimes it is the exact same product just shipping from the manufacturer in China versus from the states with their markups on top.
In the end, I am disappointed that the costs are seen as trivial to the US vendors. If Americans had to pay the costs we do for their parts, no one would be restoring their vehicles the way they do now. Ask @EuroDat and other Europeans how they feel about importing parts! And their Euro is worth more than the US Dollar!