[tehmaco]

The initial investment would be significant yes, but Mars isn't anywhere near as space constrained as much as the ISS.

Once you've got enough people and supplies, you can build farms, which means less food needs to be shipped out, freeing capacity for other goods. Presumably a lot of the infrastructure will be shipped out long before people are, so all they need to do is collect things from the supply drops, then assemble and expand.

Get the Mars colony to self sufficiency and the cost to Earth will trend to zero.