Obviously it would depend on condition. There some on Ebay for $800 or more. Id Check out Ebay and watch a couple of them and see what they are going for. Thats a nice Piece for sure.
If you're referring to a Gold Certificate with the gold seal Series of 1928 (Mellon and Woods), the Red Book (retail) shows the bill worth $800 in VF-20 (and nearly double that in EF-40). If you're lucky enough to have a 'star' bill, the value jumps to $4,500 in FV-20 condition and $12k in EF-40 (again, retail value).
Don....