i think the 20 year is probably worth about $800-900, but i wouldn't go above that based on the reviews i have heard saying it isn't a significant upgrade from the 16 year.
i have purchased several bottles of the 16 year on ebay over the past couple of years (they just keep disappearing!
) and as response to one of the naysayers higher up on this message board, i can tell you that it really is worth the money if you appreciate truly fine bourbon.
of course, i can't afford to drink the good stuff all the time, so i keep a bottle of woodford reserve (or something of similar quality) in the liquor cabinet.
just for fun, i compared the AH Hirsch 16 year (just regular gold foil top) side by side with the Woodford Reserve.
Wow. just the nose alone tells the whole story.
The Hirsch is sweet, nutty, absolutely dreamy. By comparison, the Woodford smelled like a meth lab or something. If you have the chance to do this experiment for yourself, you'll know where your money went.