I personally wouldn't go over $100 for it...probably not over $75 unless it was in like-new condition. Enlarger lenses are dirt cheap these days, and the prices are still headed south.
I picked up a Schneider 135mm Componon-S for under $70. Killer lens...for my use, I can't imagine every finding anything better. (I'm sure the APO-Schneider HM lenses perform better wide open, but how often do any of us use an enlarger lens that way?)
You've already been given the best advice: Check eBay completed auction prices. I found two of the newer versions that have sold recently: one for $100 and one for $175. Both in great shape, and both the latest Nikkor optics and coatings. The one you've got pictured (which, by the way, will almost certainly perform as well as the newest lenses if you stop down to f/8) is an older lens and shouldn't bring as much as the newer lenses. (To be honest, I was surprised by the $175 sale...there are lots of sales of good 150mm lenses on eBay for well under $100.)
Having said all of this...if the lens is worth $200 to you, go for it. But if it's really worth that much to you, you can probably buy an almost-new, recent vintage lens on eBay for the money.