If you are interested in the original concept of space colonization in Gerard K. O'Neill's vision, you will see that it's exactly because there is excessive space "in space", hence it's viable to colonize the solar system. He imagine that the total solar system population inhabited in space will be near the asteroid belt, using the design of O'Neil cylinders (about 800 km2 inside the cylinder). And the estimate population sustainable in the space colonies is about 100 trillions, and some even suggested up to 5 quintillion.
And the raw materials are everywhere. The soil in Mars are suitable for agriculture. The minerals in asteroid belt. The water on other planets and satellites are not that scarce, even the abundant Helium-3 on the moon is also valuable if nuclear fusion is available commercially. The space colonies should be self sustain units of their own. But all these seem to be far gone from people's imagination now. (except for a few and in science fiction) And their visions died out. But all the technologies to construct them already existed (even 30 years ago). It's the amount of efforts and political environment seems to disappear gradually for the last 2 decades.
P.S. The abundance of energy is one thing. To transform or transfer the energy and using it to production is anther matter. You can't transport pure energy. Or we already done that with thousands of satellites in orbit. We need somehow receive the energy back on Earth. You can not plug a super long cable from orbit to the ground. Many crazy ideas had been proposed like using giant mirrors in space and beam down super concentrated light/microwaves back to earth, but they are not that appeal under current economy. Since it's much cheaper to build solar panels on the grounds with existing infrastructures. We are still thinking and limiting by the term of "earth-bound" economy, and if space colonization really works, then the resulting economy will be very different as of right now.