A $50 billion project getting cut to $1-2 billion simply because of lower launch costs? Not in this world. NASA will likely spend several hundred million dollars developing the Mars space suits alone. I've worked on government procurement. Even with cheaper launch costs (and it'll be a long time before you cut the costs by two orders of magnitude), they'll still spend the full amount and then some. That's just how the system works.

While the basic theory of multiple redundance leading to lower costs sounds good, it also has a hude flaw. The easiest way to see the flaw is to look at the mission backwards - from end to beginning. For every pound you return from Mars, you have to launch many, many pounds on the outbound leg. All of that extra redundancy means a lot more weight, which means more fuel, which means more weight, and on and on. It takes propellant to accelerate propellant. The whole thing snowballs very quickly and expensively. That's why every ounce is so important on space vehicles in general. It'll be far more important on a manned Mars mission.