FF;
All of the Gold keys were listed for well below $1,000 in the first OPG back in 1970. The following were the four most valuable GA books:
1) Action Comics #1 - $300.00
2) Detective Comics #1 - $275.00
3) Marvel Mystery #1 - $250.00
4) Superman Comics #1 - $250.00
With respect to your other question regarding pending drops in Golden-Age books. I don't believe we will be seeing any significant drops in the GA keys due simply to the limited number of books out there. There could be drops in the mid-run mid-grade non-key GA books due to a lack of interest over time (but nothing comparable to a 96% drop in value).
Personally, I believe that the chance of a drop in value should be even higher for the newer books due simply to the higher number of books out there. Especially when you factor in the number of high-grade copies out there. This would even apply to key books such as Hulk #181. In fact, hearing figures of $50,000 for a 9.9 copy of Hulk #181 seems more ridiculous and provides more room for downside risk than an unrestored 9.4 copy of Action Comics #1 at $1,000,000.