It all depends.
First it depends on condition. If the mold has been battered with a hammer and beat up, then it's not worth it. Is it an original H&G mold, or one made by Ballisticast? Ballisticast owns the rights to the H&G molds.
The originals usually go for more money, but the Ballisticast molds I have are of good quality, but the company has changed hands more times than Elizabeth Taylor, so it depends on who actually made the mold.
If it's in good shape, then it's worth it, but if it's been abused, pass on it.
Hope this helps.
Fred