I wholehartedly agree. But, if you look over the past 50 years, the price of energy (electric) vs oil/gas is a pretty reliable ratio that has much less fluctuation and can help with assessing cost savings. If you know the fuel consumption data on the vehicles you are comparing, that is a fixed point that won't change upon purchase, so some level of fuel cost comparison over time can be safely made, albeit not precise.
There is risk in company solvency that can't be known either- but I bought from Tesla, not GM or Chrysler so I think I lowered my risk in that regard