This is nothing compared to medical software, for example. All you can lose here is some money, but no human life in danger. Some more perspective.
With that argument you could argue that any loss of money is unimportant, because it could have been used better. This amount has been invested for Mars exploration, so a mission failure would be a net loss.
Now, to be clear, I think there are plenty of good arguments that spending a marginal 2.5 billion dollars to put a robot on Mars is actually the right call, in terms of its long term benefits for humanity. Wasn't taking a position on that either way. My point is just that you can measure the cost (and, by assumption, benefits if we're successful) in units of human lives, and that it's a big number. That's wiped out if the rover crashes, so a lot is riding on that code.
You might argue that the risk of failure is priced into the tradeoff society made. You might also argue that not all of the value of sending the rover is destroyed if the landing fails. Those both seem uncompelling, but I haven't thought too hard about it.
US spending on Iraq does, in fact, really tick me off. It's an enormously inefficient use of resources.
Consider that we've lost over a third of an interplanetary mission in pointless legal battles.