An automatic pallet changer lets an operator load the next job while the machine runs the current one, and pallet pools extend that to lights-out production. Automation raises throughput and, on the used market, resale appeal. It's common on HMCs and higher-end VMCs.
See every Horizontal Machining Centers in the reference library, by make and model.
How this affects buying and selling: read The Gauge, or value any machine free at The Machine Blue Book.