Break-even volume
Beginner
The number of units at which making your own chip becomes cheaper than buying ready-made ones.
Novice
The production volume where two options cost the same in total. Below it, the option with the lower one-time cost (often an FPGA) is cheaper; above it, the option with the lower cost per unit (often an ASIC) wins.
Expert
N* = ΔNRE ÷ Δ(variable cost per unit), where the variable cost includes the unit price plus lifetime energy and any per-unit change costs. Uncertainty about future changes and schedule shifts it, often by more than the unit-price estimate.
Explained in Where FPGAs win (Architectures).
See also: NRE, TCO (total cost of ownership).