On-board Air Compressors

Bedlam wrote:
This twin tank model 120VAC has been out longer for about half the price of the single tank: https://www.harborfreight.com/air-tools-compressors/air-compressors-tanks/4-gal-2-hp-125-psi-twin-tank-air-compressor-62763.html

The HF Central Pneumatic in your link is only 125 PSI (vs. 200 PSI for the HF Fortress). HF's own product review says the Fortress offers 300% more runtime vs. a standard 125 PSI compressor. The tank(s), lines, and compressor have to be much more robust to handle the much higher pressure---thus the higher cost for the 200 PSI Fortress.