Screenshots represent as they exist currently in Beta
Keep Costs: Attachment 790
Housing Costs: Attachment 792
Stronghold Costs: Attachment 791
Stronghold Materials Needed: Attachment 793
These are available in each NPC city, with Keep and Housing vendors.
The upkeep cost for a Tier 1 Stronghold is almost 1 gold every day, and the charge starts when the initial blueprint is placed. So have your coin ready to go.
