If an independent developer can manage to keep their 70%, Microsoft has a back door approach to choke their bottom line. MS can choose at their discretion to "market" any XBLA title and take an additional 30% cut of the profits.
Some foreign XBLA developers don't even realize that they are getting screwed by Microsoft on the point-to-dollar exchange rate.
This entire process exists to basically nickel and dime every possible drop of profit from the independent developers.
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