What do you estimate the cost would be to have each tile hand drawn by an artist?

I don't think there are enough artists in the world to achieve this in a reasonable amount of time (1-5 years) and you're probably looking at a $10M cost?

Part of me wonders if you put a kickstarter together if you could raise the funds to have it hand drawn but no way the very artists you hire wouldn't be tempted to use AI themselves.