Natural gas liquefies around 3500 pounds where propane is about 150 PSI. The cost of liquefying natural gas uses as much energy as you liquefy. 50% efficiency is not good next to 100% with propane. Would you like a ride on a bus setting on high pressure flammable container? Why not drill for oil and make more refineries? That would be the easy out!
I dunno if your figures are correct, but if so it would seem that a substantial fraction of that 50% "loss" could be recovered in a turbine when the gas was used.Partial oxidation of natural gas to an alcohol would be more efficient than losing 50% of the energy to compress the gas . . .