It's listed as brand new in the box! I think they have 4 of them. I'm not sure if they have one set up to test, but I could ask. It's about a 3-hour drive away, so I can't just go have a look and then think about it.It looks well taken care of, and $400 is less than a Ridgid 6” jointer used to cost a decade or two ago.
I would want to run a hardwood board over it to test it before buying, but $400 sounds reasonable.
I presume the “150” in the model number means 6”.