Frank,
Griswold made nickel plated iron from c.1891-2 up into the 1950's. After about 1930 they went mostly with chrome plating but some nickel ("silverlike") was still offered. If your pans have the slant/Erie trademark they are c.1909-c.1916 and, if slant/EPU, they are c.1916-c.1923. The prices you mention are within reason if in good condition. I personally like the nickel plated pans since they were polished all over. They also cost exactly twice that of black iron when new. But, many people don't like the plated pieces so their prices are generally lower, especially if the plating is not good. Bad nickel plating, to me, is not nearly as undesirable as bad chrome plating.
Steve
