actually i've seen people do this a lot when they got other people wanting to partake in the league. if you want to be invited back, just make sure you're not last place. it's not that hard since last place is usually a deadbeat team. if you can't beat a deadbeat team, i don't know if you should play fantasy.
Playing for more money. When you have $50 bucks into it, you could walk away pretty easily IMO, but once you have a few hundred in you stay in it for the long haul.
But there is an answer that does not involve money, we do it every year and it works pretty well.
We have as H2H portion as well. At the start of the season the commissioner hands out sheets to each team with a weekly H2H schedule. We play a 10 team 5 x 5 roto so you can conceivably get 10 points per week (1 point per category) versus the team you are schedules against. At the end of the week we count up who won which stat and divide the points up. The Season is setup so the half way point is at the end of next week which leaves time for the playoffs. The league is usually divided into two divisions and the winner of each Half goes to playoffs, and there is one wild card team from the first and second half, so 6 teams total.
This might sound complicated but oddly enough every year the teams at the bottom somehow end up being the wild card, keeps them interested and the league competitive.
The winner of the H2H also gets half the pot. So who ever has the hottest last month can win both (only happened once but they got a few thousand).