One big difference is that there is little to no competition from the mail/internet order side. If you want a big LCD, you either go specialty local or big-box. Sites like Audioexcellence, SVS/HSU just don't exist up here, while Amazon.ca only deals in small items. Inflated prices or not, there just isn't a lot of alternatives. And for large purchases (physical size) like these, few people are willing to deal through the US due to extremely expensive shipping, brokerage fees and whatnot.
For example, Westinghouse is pretty much only carried by Best Buy up here. If you want a Westy, you buy at Best Buy, and warranty is handled through them as well.
Best Buy owns two brands up here, with Future Shop targeting higher end consumers and Best Buy targeting lower end, families. This is reflected in what is carried - if you want the largest screens and/or Energy products, only Future Shop will carry them.
Don't really see this changing much soon honestly...