I'm almost there, but not quite...
If you have $10,000 in your account and you trade 1 lot of USD/JPY with a minimum margin of $50, I dont follow how this isnt 1:200 leverage. I see that the account and open exposure are equal ($10K), but the used margin (which you equated to a downpayment for house) is still $50. To my thinking, in this example we've put up $50 for a $10K contract. $10,000 over $50 is 200, right? Why isnt this 1:200 leverage?
Thanks for bearing with me.