The price is primarily driven by the production capacity (measured in kg/h or TPD), the purity level of the output gas (e.g., Food Grade 99.99% vs. Industrial Grade), and the remaining operational lifespan of the core components. Buyers should evaluate the compressor brand (e.g., Atlas Copco, Ingersoll Rand), the condition of the purification towers, and whether the refrigeration unit uses modern, compliant refrigerants. A plant with automated PLC control systems (Siemens or Schneider) will command a higher price but offers significantly lower operational risks.