Godaddy and estibot valuations are meaningless and worthless. The only people who use them are sellers - serious buyers know they're irrelevant. The question is would YOU give him $400 right this moment for a domain you say is worth $800? Should be a no-brainer right? If so I have about $10,000 worth of domains you can buy from me this instant and make fortunes according to godaddy and estibot. If not why not?
Doing a search for "Industrial Workers" anyone can see it is a legitimate generic keyword domain. You need to get the domain setup as a landing page that can be indexed and wait for a end-user buyer to come along. The domain should fetch at least the $2k appraisal by GD to an end-user, you will get very little from a speculator given its tiny audience of labor union related buyers.