Building a space station cheaply should involve re-using all the pieces that are already made and thrown away or COTS parts that have been tested in space.
But if you tried to do that today there would be a lot of engineering to integrate those technologies. So there is room for the “operating system” company to take all the individual space “apps” and combine them into something resembling space station 2.0 and like Microsoft they may eventually emerge owning everything.
Space X has 190 m^3 of fully tested human rated volume they are sending to space in the form of Dragon modules between now and end of 2020 if there was a way to not bring them all back that would be essentially “free” space or at least very low cost relative to new design and launch to LEO. There is some real cost because the trash and return cargo from those flights would have to be brought back another way or stored. But there are ways around that too I will discuss in another post.
The issue here is the port interfaces. There needs to be interfaces lots of spare ports for Bigelow, SpaceX, ULA, etc. They need to be able to pressurize/depressurize individually and in sections and have a spacer sized to extend past the module attached so two bigalow modules don’t rub against each other for example. It wouldn’t be such a large task to build this single module that could allow a large increase in ISS size for the additional cost of 1 or 2 extra port interface modules designed and several instances flown to ISS.
The space industry is an interesting market segment one minute people are saying Bigelow has no market for their modules and the next people are saying that a new company is being formed to fight Bigelow for the exact same market and starting with exactly the pieces that Bigelow has already demonstrated. So its possible that is what is happening. But if I was trying to own the space station market I would focus on the glue and buy the cubic meters of volume. That leaves room to start to develop the solar, waste recycling, power distribution, life support etc which are not presently mature in an integrated COTS sense.
This is what it may look like