The cost of the test bonus depends on the value of the bonus that the weapon provides to your attack roll. This cost is calculated by multiplying the bonus value by 20.
If this bonus is negative (penalty), the cost becomes a reduction.
Example:
A +3 bonus will cost 60 NX.
Test Bonus Cost = 20 x Test Bonus
Reminder: The value of the test bonus of the weapon must be between -5 (penalty) and +5.