[coldtea]

>Making an effort to colonize Mars does not carry such a cost. People who are interested in solving this issue will not magically do whatever you'd like them to do instead.

The same holds true for every calculation of opportunity cost. It's not about whether you WILL do Y instead of X, but about the relative cost of doing X vs Y.

E.g. a business that does X will not "magically do Y instead" just because X incurs a big opportunity cost. But that's beside the point -- it will bear the opportunity cost whether it's willing to switch to Y or not. If the CEO is stubborn and doesn't even want to hear about Y and wants only to do X, doesn't mean the company wont suffer the opportunity cost of not doing Y.

The same holds true for humanity. If the people spending resources to go to Mars wont ever direct them elsewhere, we (as humanity) will still have an opportunity cost of going to Mars vs spending the same effort on something else.

(And it's not like that's our premise a given -- that those Mars resources can't "magically go to something else instead". Pressure on the government for example could cut NASA's budget and Space-X subsidies towards some other cause).