Envelope Paradox: A simple solution?

[TD_WONDER]

1. I know there is X {the amount} in my envelope.
2. The probability that X is the smaller of the two amounts is 1/2, and also it is a 1/2 possibility that it's the larger amount also.
3. The other envelope may contain either 2X or X divided by 2 {1/2X}
4. If X is the smaller amount the other envelope contains 2X, BUT, If X is the larger amount the other envelope contains 1/2X
5. This means, the other envelope contains 2X with the probability 1/2 and 1/2X with probability 1/2
6. So the value of the money in the other envelope is:

{1\2} * {2X} + {1\2} * {1\2X} = {5\4}X

7. This is greater than X, so, on average, I gain money by switching
8. After the swap, I can denote that content of the other envelope {Y} and reason in exactly the same way as above
9. I conclude that the most rational thing to do is to swap back again
10. To be rational I will then end up swapping envelopes forever.
11. As it seems more rational to open just any envelope than to swap indefinitely we have a contradiction