Big dreams are cheap to conceive and expensive to realize — a truism, for sure. Exactly how expensive is not always easy to determine in advance. And mustering the required resources is a daunting task. I have found a brief treatise on Mars colonization projects, a piece of macroeconomic and political science analysis by scholar John Hickman — link >>>
The colonization of Mars is an extremely long-term venture (perhaps 700 years) with immense up-front investments and uncertain returns. Hickman argues that this premise requires heavy government involvement in the early stages, because no other actors would be ready (or even able) to provide necessary resources. He points at historical parallels in the European colonization of the New World, such as the great importance of crown-sponsored trading monopolies in the early centuries, and the huge subsidies (both land grants and loans) to railroad-construction in the late 19th century by the Canadian and US federal governments.
Hickman considers the construction of the Panama Canal by the US government one hundred years ago to be an apt parallel to Mars colonization. It was an enormous public project with many spin-off advances in engineering and medicine and it brought plenty of benefits to world commerce.
One of the more tangible achievements of a permanent human presence on Mars would be improved chances for the survival of the human species in the future. If one world is lost to a cosmic disaster, another would remain.