QaiFan, when you are comparing sizes the Leaf does appear small size wise, but over the last 10 years there has been a vast variety of Leaf Battery Upgrades see the following :
The range in electric cars depends entirely on the kind of battery that is used in the powertrain. Below is a summary of the various battery sizes and ranges used in Nissan Leaf models from 2010 to the present generation :
First-Generation Nissan Leaf (2010-2017, ZE0) :
2011-2015 – 24kWh lithium-ion battery; EPA range 73-84 miles
2016 – 30kWh lithium-ion battery; EPA range 84-107 miles
The 2016 Nissan Leaf S also used the 24kWh battery
Second-Generation Nissan Leaf (2017-Present, ZE1)
40kWh lithium-ion battery; EPA range of 151 miles
62kWh lithium-ion battery; EPA range of 226 miles
Now regarding fixed costs these appear difficult to find and are mostly US related. But there is a wide variety of Battery upgrades now available over the (Leaf) last 10 years. Regarding the Ariya being so new who knows what will happen or what cost will arise.
It also depends on the Guarantee offered by the Manufacture and whether this would be a Std / Extended or a Special.
As Nissan Sunderland are now going to produce Batteries in the UK they could well become cheaper.
I have attached information for you to read and assess perhaps you can find the answer to your question - hope this helps in some way - Dave
Nissan Leaf Battery Replacement and Upgrades: Full Guide - Green Car Future :
https://www.greencarfuture.com/electric ... tery-guide
EV Rides Can Extend The Range Of Your Nissan LEAF With Battery Upgrades :
https://insideevs.com/news/428315/ev-ri ... w-battery/
Nissan will build batteries in UK to sustain Sunderland plant | Autocar :
https://www.autocar.co.uk/car-news/indu ... land-plant
2021 Nissan Ariya revealed: price, specs and release date | carwow :
https://www.carwow.co.uk/news/4655/niss ... lease-date
Nissan unveils 300-mile Ariya electric SUV with liquid-cooled battery, 130kW CCS charging, starts at $40k - Electrek :
https://electrek.co/2020/07/15/nissan-u ... d-battery/