Annual volume
Higher volume = lower unit price (tooling amortization). 10k pcs vs 100k pcs can halve per-part cost.
Material (silicone grade)
Standard silicone (lowest cost) vs FDA medical grade vs conductive silicone (highest).
Color count & complexity
Single color (lowest) vs 2-6 color pad printing vs IMD (in-mold decoration).
Backlighting
No backlight (lowest) vs light guide film vs individual LEDs per key.
Conductive pills
Carbon pills (standard) vs gold/nickel plating (higher cost, lower resistance).
Coating & surface treatment
Matte/gloss finish, anti-microbial, or UV clear coat add cost.