Nissan Leaf questions

Suzuki over a Nissan .

I think the addition of RUC's would tip the economics significantly. That said, I think the road tax system will be reworked before that point anyway. I ran the numbers below anyway.

RUC's to run a 2011 Leaf 15,000km at 6.8c/km works out to $1020. Add in electricity @15c/kWh and 190Wh/km, works out to $430. Total $1420.

Petrol (incl road tax) to run a 2011 prius at its rated 3.3L/100km over 15,000km on $2.30 petrol works out to $1138.5.

Also consider that a 2011 Prius can be purchased cheaper than a 2011 leaf. (the same also applies if you compare a new Prius with say a new Hyundai ioniq. ).

Regarding Maintenance, While a leaf requires less maintenance than a combustion engine car, the leaf is not maintenance free. For example, a leaf has coolant (antifreeze) that needs changed. (Initially at 15years or 200,000km, then every 5 years or 120,000km).

You forgot the leaf diff oil changel at 100,000km that costs 80 bucks,
low k prius command similar money to a leaf.
20 moving parts in a leaf motor compared to 2000 in
a fossil motor, more reliability with a leaf. And the biggie
better for our environment, does not all come down to
dollars and cents .

It's pretty unlikely the government will let it be cheaper to run an ICE than an EV. Either they'll charge a lower RUC rate for EVs or more likely increase the tax on fuel. I suspect an extension of the RUC exemption is probably likely, but it's all just speculation at this point.

As far as maintenance goes its only the engine/trans that has extra maintenance on a petrol/diesel vehicle . You still have to wash it, replace tyres, wiper blades, grease the suspension, replace headlight bulbs etc regardless what powers your car.
I think that it would it will be many years before we become EV only. The little people movers can easily be EV, but commercial vehicles that travel big kms just don't have time to recharge. A logging truck will often do 600km a day moving 50 tonne approx on one tankfull of diesel which takes about 10 minutes to top up.
At this stage I would hate to be in an EV at Xmas time and trying to travel say Auckland to Bay of Islands which is about 260km. If you can only manage 140km on a charge thats going to mean probably 2 charges to get there. Thats fine if you are the only EV on the road but if you happen to be the 4th to arrive at Wellsford and want a charge you are waiting at least an hour to even get plugged in. The petrol powered vehicle owner has arrived and is sitting down, feet up enjoying a beer. And if you want to tow your boat to the Bay you are spending a lot of money to buy an EV capable of doing that.
And RUC charges should be the same regardless of how your vehicle is powered as supposed to be for road maintenance and improvements and EVs have 4 wheels on the ground just the same as petrol vehicles.

"I'ts only the engine and trans that requires extra maintenance".

Your calculations (and the ones following on from it) assume that petrol/diesel prices will be similar to current by early 2022. That will be unlikely due to a variety of factors including geopolitical events, rising awareness of climate change, oil supply-demand factors, and governmental taxation and incentivisation measures. I'd sooner put my money on an energy source that can be harvested from the sun if you choose to.