The fact of the matter though is that NASA has sent 32 missions to Mars! We pretty much know almost EVERYTHING there is to now about Mars which is that it is a geologically dead planet with almost no atmosphere. Thats pretty much it. I can almost guarantee that there is no life on Mars. They may have been small biological organisms on it in the past, put everything on that planet is dead now. The moons of Saturn and Jupiter though present a real possibility of actually supporting potential extra-terrestrial life right now though! We know this because of the geological composition of these moons have elements such as oxygen, methane (biological waste product), nitrogen and so on. Saturn's moon Titan is so phenomenal because it is the only moon in our solar system that has an actual, thick atmosphere and is though to be very similar to what Earth was like billions of years ago at or before the beginning of life here on Earth. If we went there then we could learn an insane amount of information about not only our solar system, but ourselves as well.
You do make a good point that it is more costly to go there, the space craft Cassini currently orbiting Saturn is the most expensive space craft in history, but at the same time it has sent back an extraordinary amount of information regarding or solar system that we had not known about before the mission. My personal belief is that NASA should be COMPLETELY done with investing in Mars because of the insane amounts of information we already know about the planet. Honestly, how much more is there to know about the planet? I want NASA to invest the majority of their money into what is the unknown because the unknown is the ultimate when it comes to exploration, regardless of wether it be here on Earth, in our Solar System, in our galaxy, or beyond.