The game works on something called Utility Theory, Clucky. The problem with saying that is that you are assuming that a sum of money twice as great is worth twice as much to a person. Here's an example (if we were playing this for real money.)
There are two values left: The £250,000 and the 1p. You get offererd £100,000. By your logic, you shouldn't deal because the expected value is greater.
However, you have to remember that money starts to lose it's meaning at about £20,000. If you had to bet £20,000 on the flip of a coin, would you?
(Incidentally, a way to approximate this is to work out the root-mean-squared. That is, E(sqrt(X))^2 as this cancels out the dominance of the larger figures.)
You also have to remember that there are other factors affecting the board; the biggest one being the 'volatility' - basically how much the game will swing if you remove the top figure. In the final five, if you have left:
£250000; £1; 50p; 10p; 1p
then the offer will be lower than this game at the same point.
£100000; £50000; £35000; £20000; £15000
Because the 'volatility' is lower.
Also, another point to remember is that the banker doesn't always want someone to deal. By offering a low amount, you are drawing the player to carry on; and encouraging them to enter a round in which they will open a number of large numbers. I can give you a real life example for this (Trevor's game) His board was
1p; £10; £50; £35000; £250000
He got offered £9900. The banker knew the offer would have to shoot up were the quarter of a million to be left there, but he wanted to encourage Trevor to play onwards, becuase he knew there was a 60% chance that he'd take the largest number out
Although, I agree that I wouldn't have dealt at any of the boxes in this game, but just becuase of the unlucky selection. By taking out big numbers, the deal will stay low in comparison to the mean.
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I'd also like to point out the reason I'd set the final offer as what i did. There were ten ways that the final two boxes could be arranged - I pitched the offer so h alf were above and half werre below.
Nifty