I want to know the answer to the following question:
What came with lesser lesser cost mobile conversion hardware or stationary hardware?
All the background I'm provided with is that "While both systems use energy in converting higher voltage AC from the USSR's power grid to lower voltage DC, the conversions for the DC system all took place (at higher efficiency) in the railway substation, while most of the conversion for the AC system took place inside the locomotive (at lower efficiency).". Is that enough to answer the question?
Answer: no