I've seen them anywhere from $600-$1,000 depending on if you have a ported matched plenum, port matched dragon plenum, TB, etc. Can't go too crazy IMHO, once your close to $1,000 your almost half way to a used twin screw. Ported blowers don't sell like they used to a few years ago.
That's a great deal but I see it was a M122 off a 2010 GT500 and ported by MRL. I don't know what those blowers normally fetch but apples and oranges.
The "Race Port" was a Posi Performance trademark, arguably the best Eaton M112 setup you can buy. Brian stopped porting a few years ago so the blowers usually fetch top dollar as far as ported M112 Eatons go. Especially if it had a port matched Dragon TB/PL which is a $500 piece in and of its self.