I'm interested in knowing in as much detail as possible why discount
brokerage firms charge a much higher commission in Canada than in the
U.S.? Primiarly, I'm interested in knowing how the business models of
U.S. discount brokers differ to Canadians on an expense and cost focused
approach. If you're able to provide numbers and stats, even better!

Some firms to assist you on your research path include: TD Ameritrade,
E*Trade, Charles Schwab, Fidelity and Merrill Lynch.

And a really old link that may be useful which talks about potential
oppurtunity for US firms to enter into Canada:
http://strategis.ic.gc.ca/epic/internet/inimr-ri3.nsf/en/gr-98946e.html