I paid $40 for mine, it needed cleaning and servicing. It had some tension issues, but since it has a new belt and the tension fixed, it's been running beautifully. It came with the original case (smelly and musty) and a whole set of attachments: Ruffler foot, binding foot, hemmer, buttonholer and cams, zig-zag attachment and cams.
The machine is so easy to use my children have been sewing with it, making small tote bags and stuffed animals.
Personally, I wouldn't pay $150 because that's out of my price range. But, if the machine is in pristine condition, with a table in very very good condition, AND it has every single original attachment with it, then it may be worth $150 to you.
If there are any defects or issues, you may be able to use those to negotiate a better price with the seller. I found a Necchi Supernova in the back room of a local Thrift shop, and the owner said he thought it was worth $100. It was filthy, some of the cams were broken, and the cabinet needs to be completely refinished. I told him I'd give him $40 and he said "Well... for YOU I'll go $40." Personally, I think he was just glad it wasn't taking up space in his back room anymore. So it never hurts to ask if the price is negotiable.