Several online metal detector specialists offer factory-refurbished, used and open-box return models at discount prices on specialty lists. These include Kellyco Metal Detectors, as well as MetalDetector.com.
The number of refurbished metal detectors available on these websites varies, and listings are generally for a single item. As such, supply is limited, but these pages are also updated regularly with new models.
Another option for finding refurbished metal detectors is an auction website such as Ebay, which offers a more substantial selection and at more reasonable prices. However, sellers here are not necessarily specialists, and so a customer must purchase at his own risk.