This year, we're running a match point singles league within our team league. Every week is a position week, which means that #1 always plays #2, 3 plays 4, and so on. It's voluntary, but 90% of the league is participating. The cost is an extra 5 dollars a week. At the end of the season, the prize money is spread down to the bottom, so everyone gets something back. Ours is scratch (like our team league), but it could certainly be done using handicap.
Nobody gets rich, but it adds an extra element of competition, and everyone seems to really like it. I'm sure it will help with retention next year.