That's the last of the N frames prior to the firing pin being moved off the hammer and into the frame. The 5" is probably the least common of the Classic and sold for a good bit less than that new. However that was then and this is now.
I'm not aware of what they sell for now. It seems like a bit much but it only takes one person that wants it bad enough to make it worth that much.

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Lynnie, Professional Pest