The Kes problem is a non starter, if you read his post carefully his opponent discards all cards but the Ace of Spades, thus his opponent will hold the Ace 51 times out of 52 on average. hardly comparable to Deal or no Deal.
The Monty hall scenario is a red Herring, and is a totally different statistical problem, and is not comparable to Deal or no Deal.
1) Firstly Deal or no Deal uses 22 boxes not 20
2) You are given seven offers, the first after discarding 5 boxes, the remainder after discarding 3 boxes each time, until you are left with 2 boxes.
3)Your chances of HAVING the £250,000 prize after each round is as follows...
Round 1 .....17 in 22
Round 2 .....14 in 17
Round 3 .....11 in 14
Round 4 .....8 in 11
Round 5 .....5 in 8
Round 6 .....2 in 5
Round 7 .....1 in 2 ...........50:50
Multiplying the first column gives 17 x 14 x 11 x 8 x 5 x 2 x 1 =209440
Multiplying the 2nd column gives 22 x 17 x 14 x 11 x 8 x 5 x 2 =4607680
4607680 divided by 209440......gives a 1 in 22 chance of selecting the £250000 box.
Any attempt to skew the 1 in 2 chance would result in the original 1 in 22 chance being wrong, which we all know is true.
So 50:50 is correct...................