Is the cash calculator exact?
No — it is an estimator. The game does not publish official cash rates, so you enter your own numbers and the tool shows the math with stated assumptions.
What inputs does the planner need?
Waves cleared, average kills per wave, your cash-per-kill estimate, optional current cash, and your playstyle goal (damage or survivability).
How does it pick the purchase priority?
It uses a deterministic rule table: damage goals scale cheap rapid weapons first, survivability goals add defensive pieces at the wave-10 and wave-25 milestones.