As I'm a generous sort, I'll make the following offer to anyone who still believes the odds are 50/50.

If we ever meet, we each put $100 (5*$20) on the table. I'll add an extra $20 (20*$1) for luck.

I'll supply 3 identical envelopes, put the $200 in one,and $10 in each of the others.

I'll shuffle the envelopes below the table (keeping track of which is which), and then offer you the choice of 1 in 3.

Once you've chosen I'll show you tha one of the other envelopes contains £10, and pocket that envelope.

You are then left with two envelopes (one of which you have chosen). I will pocket one envelope.As you're now down to 2 envelopes, I'll take the one you haven't chosen (as clearly it's a 50/50 chance, and you've made your choice already).

I should win often enough that the extra $50 I'm putting in won't bother me.

Sound fair?