> There are people working for NASA who actually believe we will be able to launch to LEO for $55/kg.

I mean, that works fine if you have something like a space elevator:

  $ units # assuming 10cent/kWh[0]
  You have: 300 km gravity * (.1$/kWh)
  Definition: 0.081722083 US$ / kg
  You have: sqrt(G earthmass/earthradius)
  Definition: 7911.1468 m / s
  You have: (9km/s)^2 * (.1$/kWh)
  Definition: 2.25 US$ / kg
  You have: ((9km/s)^2+300 km gravity) * (.1$/kWh)
  Definition: 2.3317221 US$ / kg

So lifting stuff to LEO should cost ~2.50$/kg in energy at current retail prices. Adding (merely) a factor of twenty in overhead to actually deliver that energy is significantly more iffy, though.

0: https://www.statista.com/statistics/183700/us-average-retail...