A couple other ideas other than an 8 ball on the break. I play two leagues, a 2 person with 16 teams and a 3 person with 16 teams. Our two person has a 50/50 drawing with no limit on tickets purchased at $2 ea. Typical payout in in the $90-$110 range per night with the other half going into the year end prize money.
The 3 person league sells tickets, for $5 I think, for a 9 ball rack where if you break and make a ball, you can keep playing till you miss with payouts of so much a ball or a bigger payout if you run the rack. The hitch is if you make a ball or more, on the break, it doesn't count till you make your 1st legal shot.
Also, you can quit at any time after making your 1st legal shot, but if you decide to keep shooting after making balls, you better be sure you can make that next shot as if you miss, you lose everything. Even with many, many 600+ fargo players on that league, the pot gets extremely large at times as you still need to make a ball on the break first, and usually only one winner gets a chance at shooting. Also, not everyone that gets their ticket is the greatest player, and most importantly, pool players being the gambler's that they are, get greedy and don't always quit while they are ahead.
Some have won up to about $2000 for playing a single game of 9 ball. If the pot starts getting too big, like 3k-4kish, and the winning ticket holder breaks dry or quits at a couple hundred bucks or so winnings, they will draw a second ticket to try and pay out more winnings.