Think of it this way: Many many more billions of dollars went into killing people. What little billions is flying up to Mars and back was not spend on killing people. Besides that, Nasa spend 2.7 Billion on the mars mission, MS just spend 7.5 billion on a games publisher...
Your first point makes sense to me. The second one... well let's just say my mind distinguishes between a financial investment that will be returned via profits and the Mars situation, where they won't really earn that money back. Plus, I don't expect businesses to spend money on helping people, but I do expect taxpaying money to be used to benefit taxpayers and thos in critical need.
Do you have any idea how much society has benefited from advances made in space exploration? The internet, gps, understanding our climate, understanding how our bodies work, improvements in jet engines, finding resources on earth. And with Mars we'll get a better understanding of how our planet formed and works as well. As well as better understanding of life itself.
The money earned back from space exploration is hard to measure, but it's infinitely more than the money earned back from a business acquisition. Which is only money for one corporation, everyone on Earth benefits from space exploration.
Here are a couple direct spinoffs
Imagine how far we could have been along with green energy if we had stuck the 2.4 trillion for the Iraq war into space exploration... Heck 9 billion of that is just one of the shipments that went 'missing' on the way to Iraq. DoD budget in 686 billion of which 69 billion for war funding. Of course we also get benefits from that like hummers, better guns and cheaper oil...