Most people agree that the most expensive object ever constructed is the International Space Station. At a cost of nearly $160 billion dollars (and rising, as new sections are added), very few things even come close.
Even among other pricey space ventures, it’s an expensive price tag. To put that number in perspective, just over 10 years ago NASA estimated the cost to send astronauts to Mars. Their rough estimates put the price of a human Mars mission in the ballpark of $40 billion US dollars.