Earlier quoted context omitted.
I imagine many had a similar view of sailing across the Atlantic before word spread of riches in the New World.
The cost:benefit of colonizing the new world was immense and known prior to widespread colonization, esp. in the tropical parts. Settling mars is like colonizing the Sahara desert, except this time with no oxygen or camels.
However, in general, there are immense resources and energy sources in space that can benefit humanity. Pioneering space will also require many technological advancements that will benefit people back on Earth.
There is also the question of learning about the universe. If, for example, there was bacteria on Mars, that would one of the greatest discoveries of all time.
I don't think your comparison is fair.