I'm not Canadian, so I can't say for sure, but my understanding is that because there is a government assistance program, the higher cost for the PDM is done that way because Insulet knows the Assisted Devices Program will pay for part of it. So they are able to charge more. I don't know if they need to do that to qualify for the program, or what. But I think the reason they do it is just because they know they will get the money from the ADP.
Insulet does not actually send to Canada, they send to a 3rd part distributor (I think maybe GlaxoSmithKline) who then works with the Canadian market.
But I can say that if you get OmniPod and need to call support and need help with a Pod, they don't ever ask where you bought the PDM. And they will only ask for the PDM serial number if you are having a PDM problem, not if you are having a Pod problem. So if you are able to get a PDM in the U.S., it's possible you can use it with no problem, and nobody needs to know where you got it.
There are a few Canadian members here. Hopefully they will see this and give possible solutions.
If you want, you can move in with me, get the $300 price, and then move back to Canada. All you need to get it is a U.S. doctor, a prescription from the U.S. doctor, and a U.S. address. I got room in my basement! It's warm here, too!