Funny you mention that as i wasn't commenting on why they were different.
If you look here the Canadian Senate released a report to "explain" the price gap.
The problem is the report fails to point the finger at what is probably the single greatest reason for the price gap (the government).
Buy a pair of kids socks in most US states and you will find they are tax exempt.
Not so here, the government wants its 13% tax on that purchase (Ontario, we have HST)
Buy a winter coat in most states and only pay taxes on the "non-exempt" portion (assuming your coat is over the non-exempt amount).
Buy a winter coat in Canada, and it is 100% taxable, clearly they have no issues taxing "required" things as well.
Heck, they even tax food here (there is a very small list of "exempt" items, but only what they determine is "essential").