Hi Marc,
These tools are not highly sought collectibles. Only collectors replicating a service station would be interested, while the typical petroliana collectors may not have the display room.
These are still currently used by auto shops that do oil changes and lubrication. You might find selling to a repair shop with a lift is easier than selling to a collector.
For a new price reference, here is a link to a current vendor with similar modern equipment.
http://www.benfordfueling.com/shop/wasteoildrains.html
