I think the main problem is that the average savings, even if correct, is not relevant to many. Most buyers want to know THEIR savings, which as we have seen could vary quite a bit.
I think Tesla could accomplish their goals (to make people aware of the savings - the car is not as expensive at it seems, and the difference is larger than most people guess) better, and get rid of the complaints, if they simply show the actual price next to a button that says "See how much you can save!" that takes them to a calculator that asks their current MPG (or if they already have an EV) and miles per year. Bonus points for asking if they are likely to receive the federal tax credit, and applying state incentives if any.