I actually did do some back of the envelope figures before purchasing.
We do around 15 000kms per year. Consumption of our old diesel car was (generously) 8.2l/100kms, giving fuel cost over a 5 year period of about $12 000. Based on the same number of kilometres over a 5 year period, I expect the cost of charging our ev will be less than $1000. Mind you, this is the opportunity cost of charging it. It may well be less than that given the falling solar feed-in tariffs. Already my energy retailer gives away 3 free hours in the middle of the day.
If I keep the car for at least 15 years (which is our habit and seems to be realistic with regards to battery life, but that's an argument for another day), then I will have saved approximately $33 000 in fuel over an ICE vehicle. I fully expect the ev to have no value after 15 years but I don't think anyone could say that the residual value of a similarly priced ICE vehicle will have a value of $33 000 after 15 years either.
IMO servicing costs and tyre costs are not yet fully computable. I would expect the ICE vehicle to have greater servicing costs. Perhaps the ev will have greater tyre costs.
So I think it's horses for courses. An ev suits us perfectly for our circumstances. If I drove long distances and/or relied on commercial charging, as much as I like my ev, I would have opted for an ICE at this stage in the evolution of evs and charging technology in Australia.
