> KataGo and Leela Zero and all the other AIs certainly didn't cost that much
And you base that claim on what exactly? Leela Go is trained by the community, which donates self-play resources. Just because you outsource your cost to volunteers doesn't mean it's free!
In order to get to a realistic estimation, you'd need to get the average cost for electricity, hardware cost (proportionate to use), and of course opportunity costs.
Since you cannot do that, I'd argue that you have no clue what the true training cost of these projects compared to on-demand/cloud costs really are.