The Merge a Nuke upgrade calculator should compare the next spend by cost, effect, bottleneck, and recovery time. Exact ROI output waits for verified prices and formulas.
Calculator inputs
A Merge a Nuke upgrade calculator needs current cash, upgrade levels, upgrade prices, expected effect, current income, board capacity, and player goal. The same upgrade can be good for one player and weak for another.
ROI is goal-based
Spawn tier, spawn speed, max spawn, cooldowns, and defense do not solve the same problem. A calculator should not rank them as if every player has the same goal. The first question is whether you want income, rebirth speed, raids, or defense.
Current recommendation
Until verified values are available, use the upgrade guide. It identifies the bottleneck and chooses the next upgrade by practical effect. The Merge a Nuke upgrade calculator will become exact only when prices and formulas are checked.
Source policy
Any published ROI table should include a patch date and assumptions. Otherwise, update changes can quietly make the table wrong.