The equation that I use isPrices of available EV's in Sweden right now, base model, starting price:
Nissan Leaf: $33500
Maxda MX-30: $36650
Toyota bZ4X: $51170
KIA EV6: $56500
Ford Mustang Mach E: $59500
so... using used parts, and my own "free" labour, you're saying I can't get it built for less than $33500?
If you can DIY then it will cost twice as much as a second hand Leaf - and be half as good as a car
If you have to pay somebody then it will cost twice as much as a brand new Tesla - and be half as good as a second hand Leaf
twice as much as a second hand Leaf - how much is a 10 year old Leaf in Sweden??
Converting is like "Hot Rodding" - do it because you want to - not to save money
The very first thing that you need to do is to check that you will be permitted to drive your converted machine
Some countries its quite easy to get a modified car on the road
Some countries its nearly impossible to get a modified car accepted for road use
You need to check YOUR country