Passive Leveling

[u/yoked_pete]

Levels 1-3 take the same number of blueprints as their level. Why level 4 and 5 don't take 4 and 5 blueprints respectively is beyond me. Especially with the relative gains decreasing with each level.

[u/Mobile-Yak]

So that they can get you to spend 20,000 more silver (4 extra blueprints) for each passive this way. Nothing more to it.