Beyond that, you are rapidly approaching the point where you are likely to
spend more on development than you will save on launch costs.
--

How is this mission to mars different then then staying on the mir for a
long dururation? Ok the russians can ship extra's to the mir at almost
anytime but still they don't count on it.

But they also have a closed enverioment. Like earth to mars would have. You
could just buy Russian data on this info not?