I think it depends a lot what you're buying. If you want an 80kWh pack like a Tesla, then yeah, that's going to be $10k or whatever, but a lot of BEV conversion projects are looking more at an around-town car anyway, where a 50km range might be adequate, especially as a starting point while you get everything else working.

So yeah, if that's your target, then you can build a much smaller and cheaper pack out of prismatic cells, eg:

https://evsource.com/collections/calb-1/products/calb-100ah

So like, 20 of those is $2800 and would get you 6.4kWh (range of like 30-40km).