set the cost of "replies" in our territories?
Yes it could be. I think the author should also be cut into reply costs though.
have you considered what you'll do when bitcoin 2x, 3x etc in price?
No not really. If the fiat price of bitcoin increases, every sat you earn will also go up in fiat price.
In the future we plan to allow territory founders to sell sub-territories within their territory which can be sold at a price of their choosing, eg 10k/mo. At that point 100k/mo is just the price for a top-level territory.