Well... personally... when I see an item advertised with the price being "FIRM" and an asinine number attached to it... I generally don't bother wasting my time. If it's a reasonable number... I might enquire. 'FIRM' generally means to me that the seller is asking more than it's worth and has no intention of selling.
Beyond that... as far as I'm concerned, the only things that matter are what it's worth to the buyer and what the seller is willing to take for it... not what he thinks it's worth, what he has invested in it... not what one down the road sold for, etc.
I bought a machine this winter that was listed at 28K. I paid 22K. In a certain market it's probably worth 40-45K.... but not in this market. Not what I wanted to pay. So... through conversation we found his bottom dollar which was more than I offered...
If you don't want to sell it, leave it in the shed. It's no loss to anyone else.