Here are some thoughts which came to my mind:
1. Does it make sense to add a filter button to the map, so borders/prices are visible in full map mode? This might make planning of claiming costs easier and the player gets a better overview what costs/route to a new resource is useful.
2. Is there a mechanic checking that the stack sizes of the costs will always fit in the players inventory?
- Since some mods also alter the inventory size to a smaller starter inventory size this might be interesting to consider.
- Some items might not stack at all, so if you have a mod with item X (stacksize 1) and a calculated cost for a territory demanding 50 of item X while the inventory size is 40, the territory might be unpurchasable. Maybe I am just overthinking this... :-)

1 - I think I can add a map tag to the map overview... with an icon and a text to show all required items... it is possible
2 - excelent problems anticipations... =) I still don't have this mechanic. I can do that, for next version. thanks