Even cheap chargers use switching supplies that are ~70% efficient from wall to battery, efficiencies as high as 95% as possible with better circuits. Battery efficiency is quite good for Li- and Ni-cells (at modest charge rates), though cell balancing can waste charge if the cells are at different charge states. Resistive losses in the wiring (e.g. 0.7% in the cord between my charger and battery, less for the wall cord) account for insignificant costs when you realize they are three orders of magnitude below the costs of maintenance. Overall, I'd call the charging process moderately to highly efficient.

I originally included efficiency in my cost estimate but realized it was pointless since the result is still at least an order of magnitude less than battery replacement and therefore does not matter. If you prefer to call it 300 miles per dollar, be my guest, but it won't make a meaningful difference. The variability in battery cost and lifetime estimates will dwarf it.