Tying the treasury cap to city-count also provides an avenue for an easy project addition: a national treasury that buffs the per-city cash cap.
For example: At 33 cities, a base $100k/city cap allows me $3.3m unraidable; a project that buffs the per-city treasury cap by 50% allows me $4.95m unraidable; a project that buffs the per-city treasury cap by 100% allows me $6.6m unraidable.
Again, let's refer to precedent and the current game rules.
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