ESS, an economical space station

Is the international space station, ISS, worth its 100 billion dollar price tag? Unless the alpha magnetic spectrometer finds something spectacular the answer is probably no.  So what would an economical space station, an "ESS", look like?  Numerous trade studies suggest to me that it would have a "permanent" core providing electrical power, cooling, guidance, communications/data transfer, robotics, life support and living facilities for 2 or 3 astronauts, an airlock, propulsion, etc.  The ESS would be man tended, not permanently manned, but might support an experiment on long term "closed cycle" life support systems.  Many of the ESS's experiments would come as temporary/replaceable plug in modules rather like the russian MRM-2 on the ISS.  The ESS would be resupplied by something similar to the russian Progress freighters which would serve to dump garbage as well as provide upmass capability.  A Soyuz like shuttle (but without the Orbital Compartment which is not needed for short duration flight to and from the ESS) would bring up astronauts as well as bring back down mass.  These shuttles could fly up unmanned in order to increase down mass capability.