BB is 6,000. 2 callers. I go all in (36,000) on the button with AKo. Also included in the bet are about 30,000 in bounty chips which can't be used till the final table. I'm fairly sure that was the right move on a short stack with a premium hand. Everyone folds except a big stack (>120,000) with 57o. I am a tight player so big stack knows I have him beat before the flop. AKo is ahead of 57o 63/37% before the flop according to poker stove. And he is a good player. Even with much less than AKo I still had a good lead before the flop. As I look at the numbers it seems his pot odds (counting the bounty chips, blinds, and other caller) might be better than 2:1. Is that the reason for the call or might there be other factors?
No, he should have folded. :-)
So there are 3,000 (SB) + 6,000 (BB) + 12,000 (2 callers) + 30,000 (bounty chips) + 36,000 (your stack) chips in the pot. That works out to 87,000 chips. It is 36,000 chips for him to call (unless he was one of the original callers) which is 2.41:1 (or 41% of the pot). This basically gives him a negative value of about 4%, or 1,440 (of the 36,000 chips that he is risking) that he will lose, on average, with this particular hand match up.
Since you have 6 big blinds, you should be going all in with more hands than just AK so the caller should put you on a range of hands that varies based on his experience and his view of the tournament/you. Since most of those hands will be pairs bigger than his cards or two overs (especially since you are a tight player), his odds won't really be any better than that ever, and sometimes much worse (your pairs).
If he knew that you had AKo, this is a marginal fold, which he could have gotten wrong "in the heat of battle" with all of the chips flying around, or maybe he just felt like gambling. However, because you could have also had pairs, this should have been a clear fold and was probably just a player who didn't make a very good decision, for whatever reason (he isn't very good, he needed to leave to meet his girlfriend and was just trying to finish the tournament, etc.).
On the contrary of the answer above, the answer is yes, is the right move. Calling 36000 to win 87000 means that you have must have at least 29% if equity. The hands that has this equity against AK are
22+, A2s+, KTs+, Q2s+, J2s+, T2s+, 92s+, 82s+, 72s+, 62s+, 52s+, 42s+, 32s AKo, Q2o+, J2o+, T2o+, 92o+, 82o+, 72o+, 62o+, 52o+, 42o+
even taking in to account the bubble factor and the ICM, the call is correct.
From a most general point of view you are able to go all-in from the Button with 9 BB, with almost 36% of hands. In this general case an opponent would had call with almost any two cards.
It seems that your opponent's play is a "concession" that you are the better player, and that he is trying to win using his bigger stack.
You have 36,000, he has 120,000, and matches you all in when his chances compared to yours are 3 to 5. There is a 3/8 chance that you will lose on this round. If you win, you double up to 72,000, but he's got you covered with 120,000-36,000= 84,000, and will try to put you all-in again.
The chances of your "surviving" (winning both rounds) are only (5/8)*(5/8)= 25/64, or less than 50-50. If your opponent is an inferior player, he'd have to like those odds.
Another way of looking at it, he goes "all in" with you for 36,000, with a 3/8 chance of breaking you. If you survive, he plays "rationally," with 84,000 chips to your 72,000. Let's say for the sake of argument that the odds are now 50-50, with your superior skill outweighing his greater chips. Your chances to win overall are only 5/16th (one half of your 5/8th chance of survival). And if he had more than 120,000 chips, there is some number X greater than 120,000 for which this would be good play.