Forget it, 1 bill then about 30 mill for about 8 drafts. Don`t upgrade imo. that is all. Ty

Drafts are based on the amount of armies earned during the level and armies per second. The sliding portion scales to up to 15% of total armies earned. That being said the draft artifact feels weak when you can get 300% increased drafts from advancements relatively easily and as you said, on most levels you hit the limit after a few drafts.

Thanks for the info. Now I understand and will discard it for a legendary upgrade for tw or ts. Seems not worth upgrading.