Pick Your Payout

Ok, we had to do A LOT of tricky math to figure out how the house always wi...err...how to optimize this game for the best user experience.  Right.  Here it is:
 
Choose a dollar denomination you want to wager, then get all your friends to throw in, too, because the more people play, the higher the winning multiplier goes!  More on that below.
 
A random number generator will be used to pick a winner.  The winner receives an amount equal to their bill times the multiplier.  The more entries, the higher the multiplier!
 
Buying more than one bill raises your chances of winning AND raises the multiplier, so go nuts!  But keep in mind that each bill is considered a separate entry, so you will only receive the winning bill times the multiplier, not your total buy-in times the multiplier.
 
The multiplier will be calculated as follows:
20 participants: 2x multiplier
30 participants: 3x multiplier
40 participants: 4x multiplier
...and so on in that fashion until...
80 participants: 10X MULTIPLIER!!!
 
Again, each bill counts as a separate entry, raises your chances of winning, and counts towards the multiplier!