I got these from Harris Seeds for $270 new. It has been lightly used and is in excellent condition. Asking $100. Pick up in Petaluma, near downtown.
From the Harris website description: Start thousands of plants in a small area! Pro Grow heat mats are made of heavy duty rubber giving you years of use and dependability. Mats provide even bottom heat for best germination and for rooting cuttings. Each mat accommodates 5 standard flats allowing you to start hundreds to thousands of seedlings in a small area. Mats must be used with a thermostat controller. Manufacturer 90 day warranty. (It is normal for mats to give off a rubbery smell for first couple days of use.)