250 years ago, you could make this exact argument about the British colonization of Australia, and it would be entirely correct. The early colony was a pure fiscal drain on Britain with almost no return.

Yet today it's the 13th largest economy on earth.

Think on a longer time scale.

The difference is that Australia is on earth... where we all live.

In fact, Australia already had people living on it.

Australia was built by forced and indentured labour.

>Think on a longer time scale.

On a longer timescale would it only be spaceX on Mars?

We also have a lot of easily accessible resources via agriculture and mining, things Mars does not have. And even if it did having mining potential, the cost of returning the goods to Earth would be wild.