from time to time, bottles for the 1920-30s are on sale. For scotch blends, it is in the range of US$200-300 for high-medium neck level spirit. If the filling level is low, deduce at least 20-30%.
Seagram was a common and largely distributed whisky in the US, so I would guess that US$150-200 would be a good estimate. Of course, If the bottle is locally sought after, you might hope to sell it for $300-400.