Cloudspire
How much Source does it cost to add two upgrade chips to a spire in one build action?
The rulebook spells out the per-upgrade cost formula directly.
- Cloudspire rulebook · Rulebook · Build Phase
Each range or attack upgrade costs Source equal to the number of upgrades the spire has after adding it, and each fortification costs 2 Source. So adding two attack or range chips to a spire that already has two upgrades costs 3 plus 4, or 7 Source in total.