How about give all of your potential clones a vote, even though you can't communicate?

So, in one case, 18 of you would say "Yes, take the bet!" and 2 would say "No, let me keep my money." In the other case, 18 would say no and two would say yes. In either case, of course, you're one of the ones who would vote yes. OK, that leaves us tied. So why not let everyone's vote be proportional to what they stand to gain/lose? That leaves us with 20 * -3 vs. 20 * 1. Don't take the bet.

(Yes, I realize half the people that just voted above don't exist. We just don't know which half...)