The price is primarily driven by the production speed (typically 3,000 to 15,000 pcs/hour) and the degree of automation. High-end models feature automatic paper feeding, precise folding mechanisms, and rotary gluing systems. You should verify the paper weight compatibility (usually 70-150g/m²) and whether the machine supports multi-functional folding for different envelope styles like pocket, wallet, or diamond shapes. Ensure the motor uses frequency conversion speed control for stability and energy efficiency.